Apparatus and method for layout of magnetic field sensing elements in sensors

ABSTRACT

An apparatus includes groups of magnetic tunnel junctions, where the magnetic tunnel junctions in each group are arranged in rows, the magnetic tunnel junctions in each row are connected in series, and the rows are connected in parallel. The apparatus further includes a first conductive layer including conductive interconnects, a second conductive layer including straps, and a third conductive layer including field lines, each field line configured to generate a magnetic field for configuring an operating point of a corresponding subset of the magnetic tunnel junctions in each group based on a current flow through each field line. The magnetic tunnel junctions in each group are disposed between and connected to a corresponding one of the conductive interconnects and a corresponding one of the straps. The second conductive layer is disposed between the first conductive layer and the third conductive layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to U.S. Provisional PatentApplication No. 62/025,966 filed Jul. 17, 2014, the contents of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to magnetic field sensors and, moreparticularly, to magnetic field sensors including arrays of magneticfield sensing elements configured to sense a magnetic field.

BACKGROUND

Magnetic field sensors can exhibit various characteristics of anexternal magnetic field. There is a range of applications for magneticfield sensing with a wide range of output voltage, current, and/or powerrequirements. It can be desirable to amplify the output of these sensorsto sufficiently high levels while avoiding breakdown of devices withinthese sensors, and while being robust against failure of individualdevices within these sensors. It is also desirable to have a scalabledesign approach for these sensors. It is also desirable to integratethese sensors into systems that can leverage their capabilities.

It is against this background that a need arose to develop the magneticfield sensors including arrays of magnetic field sensing elementsconfigured to sense a magnetic field and related methods describedherein.

SUMMARY OF THE INVENTION

An apparatus includes groups of magnetic tunnel junctions, where themagnetic tunnel junctions in each group are arranged in rows, themagnetic tunnel junctions in each row are connected in series, and therows are connected in parallel. The apparatus further includes a firstconductive layer including conductive interconnects, a second conductivelayer including straps, and a third conductive layer including fieldlines, each field line configured to generate a magnetic field forconfiguring an operating point of a corresponding subset of the magnetictunnel junctions in each group based on a current flow through eachfield line. The magnetic tunnel junctions in each group are disposedbetween and connected to a corresponding one of the conductiveinterconnects and a corresponding one of the straps. The secondconductive layer is disposed between the first conductive layer and thethird conductive layer.

Other aspects and embodiments of the invention are also contemplated.The foregoing summary and the following detailed description are notmeant to restrict the invention to any particular embodiment but aremerely meant to describe some embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of some embodimentsof the invention, reference should be made to the following detaileddescription taken in conjunction with the accompanying drawings.

FIG. 1 illustrates a perspective view of a magnetic field sensing array,according to an embodiment of the invention.

FIG. 2A illustrates a logical block diagram of a magnetic field sensingarray, according to an embodiment of the invention.

FIG. 2B illustrates a logical block diagram of a magnetic field sensingmodule including the magnetic field sensing array, according to anembodiment of the invention.

FIG. 3 illustrates a perspective view of a magnetic field sensingelement and supporting circuitry that may be included in the magneticfield sensing module, according to an embodiment of the invention.

FIG. 4 illustrates an example of a response curve relating an outputsignal of the magnetic field sensing module to an operating pointdefined by an input signal to the magnetic field sensing module,according to an embodiment of the invention.

FIG. 5 illustrates a logical block diagram of a magnetic field sensingdevice showing one of multiple magnetic field sensing modules includedin the magnetic field sensing device, according to an embodiment of theinvention.

FIG. 6 illustrates a layout view of a magnetic field sensing deviceincluding a configuration of magnetic field sensing modules, accordingto an embodiment of the invention.

FIG. 7 illustrates storage magnetization directions and sensemagnetization directions of magnetic field sensing elements in thepresence of a first anti-parallel external magnetic field, according toan embodiment of the invention.

FIG. 8 illustrates storage magnetization directions and sensemagnetization directions of magnetic field sensing elements in thepresence of a second anti-parallel external magnetic field, according toan embodiment of the invention.

FIG. 9 illustrates a top view of a portion of the magnetic field sensingdevice of FIG. 6 including a top view of a pair of magnetic fieldsensing modules included in the portion of the magnetic field sensingdevice, according to an embodiment of the invention.

FIG. 10 illustrates an expanded layout view of the pair of magneticfield sensing modules of FIG. 9, according to an embodiment of theinvention.

FIG. 11 illustrates a cross-sectional view of a portion of one of thepair of magnetic field sensing modules of FIG. 10, according to anembodiment of the invention.

FIG. 12 illustrates a top view of a portion of the magnetic fieldsensing device of FIG. 6 including a top view of a pair of magneticfield sensing modules included in the portion of the magnetic fieldsensing device, according to an embodiment of the invention.

FIG. 13 illustrates an expanded top view of the pair of magnetic fieldsensing modules of FIG. 12, according to an embodiment of the invention.

FIG. 14 illustrates an example of a response curve relating an outputsignal of the magnetic field sensing module in the embodiment of FIGS.12 and 13 to an input signal to the magnetic field sensing module in theembodiment of FIGS. 12 and 13, according to an embodiment of theinvention.

FIG. 15 illustrates a top view of a portion of the magnetic fieldsensing device of FIG. 6 including a top view of a pair of magneticfield sensing modules included in the portion of the magnetic fieldsensing device, according to an embodiment of the invention.

FIG. 16 illustrates an expanded top view of the pair of magnetic fieldsensing modules of FIG. 15, according to an embodiment of the invention.

FIG. 17 illustrates an example of a response curve relating an outputsignal of the magnetic field sensing module in the embodiment of FIGS.15 and 16 to an input signal to the magnetic field sensing module in theembodiment of FIGS. 15 and 16, according to an embodiment of theinvention.

FIG. 18 illustrates a cross-sectional view of a portion of one of thepair of magnetic field sensing modules of FIG. 16, according to anembodiment of the invention.

FIG. 19 illustrates a logical block diagram of a system for transmissionand reception of a signal encoded in a quadrature modulated magneticfield, according to an embodiment of the invention.

FIG. 20 illustrates an apparatus configured in accordance with oneembodiment of the present invention.

FIG. 21 illustrates an apparatus configured in accordance with anotherembodiment of the present invention.

DETAILED DESCRIPTION

Definitions

The following definitions apply to some of the aspects described withrespect to some embodiments of the invention. These definitions maylikewise be expanded upon herein.

As used herein, the singular terms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to an object can include multiple objects unless thecontext clearly dictates otherwise.

As used herein, the term “set” refers to a collection of one or moreobjects. Thus, for example, a set of objects can include a single objector multiple objects. Objects of a set also can be referred to as membersof the set. Objects of a set can be the same or different. In someinstances, objects of a set can share one or more commoncharacteristics.

As used herein, the terms “substantially” and “substantial” refer to aconsiderable degree or extent. When used in conjunction with an event orcircumstance, the terms can refer to instances in which the event orcircumstance occurs precisely as well as instances in which the event orcircumstance occurs to a close approximation, such as accounting fortypical manufacturing tolerances or variability of the embodimentsdescribed herein.

As used herein, the term “adjacent” refers to being near or adjoining.Adjacent objects can be spaced apart from one another or can be inactual or direct contact with one another. In some instances, adjacentobjects can be formed integrally with one another.

As used herein, the terms “connect,” “connected,” and “connection” referto an operational coupling or linking. Connected objects can be directlycoupled to one another or can be indirectly coupled to one another, suchas via another set of objects.

As used herein, the term “main group element” refers to a chemicalelement in any of Group IA (or Group 1), Group IIA (or Group 2), GroupIIIA (or Group 13), Group IVA (or Group 14), Group VA (or Group 15),Group VIA (or Group 16), Group VIIA (or Group 17), and Group VIIIA (orGroup 18). A main group element is also sometimes referred to as as-block element or a p-block element.

As used herein, the term “transition metal” refers to a chemical elementin any of Group IVB (or Group 4), Group VB (or Group 5), Group VIB (orGroup 6), Group VIIB (or Group 7), Group VIIIB (or Groups 8, 9, and 10),Group IB (or Group 11), and Group IIB (or Group 12). A transition metalis also sometimes referred to as a d-block element.

As used herein, the term “rare earth element” refers to any of Sc, Y,La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

Detailed Description of Embodiments of the Invention

FIG. 1 illustrates a perspective view of a magnetic field sensing array100, according to an embodiment of the invention. FIG. 2A illustrates alogical block diagram of a magnetic field sensing array 100, accordingto an embodiment of the invention. FIG. 2B illustrates a logical blockdiagram of a magnetic field sensing module 200 including the magneticfield sensing array 100, according to an embodiment of the invention.Referring to FIGS. 1, 2A, and 2B, the magnetic field sensing array 100may include one or more magnetic field sensing elements 102. In theembodiment of FIG. 1, the magnetic field sensing elements 102A and 102Bare shown connected by a conductive strap 120. In one embodiment, themagnetic field sensing elements 102 are implemented as magnetic tunneljunctions (MTJs). The magnetic field sensing elements 102 may bereferred to as magnetic logic units (MLUs).

For example, referring to FIG. 10, arrays of large numbers of magneticfield sensing elements 102 are contemplated. In the example of FIG. 10,these magnetic field sensing elements 102 may be arranged in an arraywith Np parallel rows of magnetic field sensing elements 102, each rowhaving Ns magnetic field sensing elements 102 in series. This array maybe compact. For example, 50,000 magnetic field sensing elements 102 mayfit in a footprint with an area in the range from about 0.1 to about 0.5square millimeters.

The magnetic field sensing array 100 may be an N-terminal device, whereN is four, five, six, or a larger integer number of terminals. Referringto FIG. 2A, in one embodiment the magnetic field sensing array 100 maybe a four-terminal device having input terminals 202 and 203 and outputterminals 204 and 206. None of these four terminals is in common withany other of these four terminals. (For example, neither of the inputterminals 202 and 203 need to share a ground connection with either ofthe output terminals 204 and 206.) Each of the four terminals may beconcurrently connected to distinct portions of a surrounding circuit.

The magnetic field sensing module 200 shown in FIG. 2B is one example ofhow the magnetic field sensing array 100 can be used as a building blockof magnetic field sensing devices. A magnetic field sensing device, forexample, can determine either or both of magnitude and direction of anexternal magnetic field incident on the magnetic field sensing device. Amagnetic field sensing device also responds to variations in frequency,phase and amplitude of an external magnetic field. Referring to FIGS. 1and 2B, an input signal 130 may be applied to the magnetic field sensingmodule 200 through a field line 112. Referring to FIG. 2A, the inputsignal 130 may be applied to the first terminal 202. The input signal130 may be a DC bias signal that configures an operating point of themagnetic field sensing module 200 by configuring an impedance of each ofthe magnetic field sensing elements 102, and also a combined impedanceof the magnetic field sensing array 100, in the absence of externalmagnetic field 140. For example, the input signal 130 may be an input DCbias current that flows through the field line 112, where the inputcurrent generates a magnetic field that couples to each of the magneticfield sensing elements 102 to configure the impedance of each of themagnetic field sensing elements 102 in the absence of the externalmagnetic field 140, and thereby to configure the operating point of themagnetic field sensing module 200.

In one embodiment, the external magnetic field 140 changes impedance ofone or more of the magnetic field sensing elements 102, and also thecombined impedance of the magnetic field sensing array 100. The combinedimpedance of the magnetic field sensing array 100 can vary due to anexternal magnetic field 140 that is substantially constant, or due to anexternal magnetic field 140 that varies with time. An amplified outputsignal 132 of the magnetic field sensing module 200 may flow throughoutput line 116, and may be measured across output terminals 204 and206. The magnetic field sensing module 200 may include bias circuitrythat supplies DC power, and that facilitates setting an input-outputtransfer characteristic and an operating point for the magnetic fieldsensing module 200, such as by setting the DC input current. The biascircuitry may include circuitry 208 that supplies a DC bias current 210to facilitate generation of the output signal 132. However, the magneticfield sensing array 100 itself may not contain any silicon transistors,as none are needed to drive each magnetic field sensing element 102. Themagnetic field sensing array 100 may be solely driven externally throughits input and output terminals.

Referring to FIGS. 1 and 2B, an individual magnetic field sensingelement 102 implemented as a single MTJ cell may, in one example, have apower attenuation of about −2 dB. At the same time, the feed forwardcoupling capacitance between input and output of each magnetic fieldsensing element 102 is very small. To increase the gain of the magneticfield sensing module 200 while maintaining a very small couplingcapacitance, many magnetic field sensing elements 102 may be linkedtogether. In one embodiment, arrays of magnetic field sensing elements102 are used to design magnetic field sensing modules 200 that canprovide large gains, such as for providing a high voltage output inresponse to the external magnetic field 140, and extended cutofffrequencies, such as for providing an output that includes frequencyvariations corresponding to high frequency variations in the externalmagnetic field 140.

Referring to FIG. 1, the magnetic field sensing element 102 can beimplemented with one magnetization, namely a storage magnetization 146,that is aligned in a particular stored direction. The magnetic fieldsensing element 102 can be implemented with another magnetization,namely a sense magnetization 144, that is aligned by a magnetic fieldgenerated by the input current corresponding to the input signal 130.This type of magnetic field sensing element 102 is known asself-referenced. Alternatively, the magnetic field sensing element 102can be implemented with the storage magnetization 146 and a referencemagnetization.

The magnetic field sensing element 102 includes a sense layer 104, astorage layer 106, and a layer 908 (see FIG. 3) that is disposed betweenthe sense layer 104 and the storage layer 106. Other implementations ofthe magnetic field sensing element 102 are contemplated. For example,the relative positioning of the sense layer 104 and the storage layer106 can be reversed, with the storage layer 106 disposed below the senselayer 104.

FIG. 3 illustrates a perspective view of the magnetic field sensingelement 102 and supporting circuitry that may be included in themagnetic field sensing array 100, according to an embodiment of theinvention. Referring to FIGS. 1 and 3, each of the sense layer 104 andthe storage layer 106 includes, or is formed of, a magnetic materialand, in particular, a magnetic material of the ferromagnetic type. Aferromagnetic material can be characterized by a substantially planarmagnetization with a particular coercivity, which is indicative of amagnitude of a magnetic field to reverse the magnetization after it isdriven to saturation in one direction. In general, the sense layer 104and the storage layer 106 can include the same ferromagnetic material ordifferent ferromagnetic materials. As illustrated in FIG. 1, the senselayer 104 can include a soft ferromagnetic material, namely one having arelatively low coercivity, while the storage layer 106 can include ahard ferromagnetic material, namely one having a relatively highcoercivity. In such manner, a magnetization of the sense layer 104 canbe readily varied under low-intensity magnetic fields generated inresponse to the input signal 130, while a magnetization of the storagelayer 106 remains stable. Suitable ferromagnetic materials includetransition metals, rare earth elements, and their alloys, either with orwithout main group elements. For example, suitable ferromagneticmaterials include iron (“Fe”), cobalt (“Co”), nickel (“Ni”), and theiralloys, such as permalloy (or Ni₈₀Fe₂₀); alloys based on Ni, Fe, andboron (“B”); Co₉₀Fe₁₀; and alloys based on Co, Fe, and B. In someinstances, alloys based on Ni and Fe (and optionally B) can have asmaller coercivity than alloys based on Co and Fe (and optionally B). Athickness of each of the sense layer 104 and the storage layer 106 canbe in the nm range, such as from about 1 nm to about 20 nm or from about1 nm to about 10 nm. Other implementations of the sense layer 104 andthe storage layer 106 are contemplated. For example, either, or both, ofthe sense layer 104 and the storage layer 106 can include multiplesub-layers in a fashion similar to that of the so-called syntheticantiferromagnetic layer.

In another embodiment, the magnetic field sensing element 102 mayinclude the storage layer 106 and a reference layer instead of the senselayer 104, with the layer 908 disposed between the storage layer 106 andthe reference layer. Each of the reference layer and the storage layer106 includes, or is formed of, a magnetic material and, in particular, amagnetic material of the ferromagnetic type, the characteristics ofwhich are described previously. In general, the reference layer and thestorage layer 106 can include the same ferromagnetic material ordifferent ferromagnetic materials. The reference layer is different fromthe sense layer 104 in that the reference layer typically has a highcoercivity, such as a coercivity higher than the storage layer 106.

The layer 908 functions as a tunnel barrier, and includes, or is formedof, an insulating material. Suitable insulating materials includeoxides, such as aluminum oxide (e.g., Al₂O₃) and magnesium oxide (e.g.,MgO). A thickness of the layer 908 can be in the nm range, such as fromabout 1 nm to about 10 nm.

Referring to FIGS. 1 and 3, the magnetic field sensing element 102 alsoincludes the pinning layer 910, which is disposed adjacent to thestorage layer 106 and, through exchange bias, stabilizes the storagemagnetization along a particular one of the pair of directions when atemperature within, or in the vicinity of, the pinning layer 910 islower than a temperature T_(BS). The temperature T_(BS) can correspondto a blocking temperature, a Neel temperature, or another thresholdtemperature. The pinning layer 910 unpins, or decouples, the storagemagnetization direction when the temperature is at, or above, theblocking temperature T_(BS), thereby allowing the storage magnetizationdirection to be switched to another one of the pair of directions.

In one embodiment, such a pinning layer is omitted adjacent to the senselayer 104, and, as a result, the sense layer 104 has a sensemagnetization direction that is unpinned and is readily varied, with thesubstantial absence of exchange bias.

In another embodiment, as previously described, the magnetic fieldsensing element 102 includes a reference layer instead of the senselayer 104. In this embodiment, an additional pinning layer may bedisposed adjacent to the reference layer. This additional pinning layermay be characterized by a threshold temperature T_(BR), withT_(BR)>T_(BS). The temperature T_(BR) can correspond to a blockingtemperature, a Neel temperature, or another threshold temperature.Through exchange bias, this additional pinning layer stabilizes thereference magnetization along a substantially fixed direction attemperatures lower than the threshold temperature T_(BR).

The pinning layer 910 (and the additional pinning layer disposedadjacent to the reference layer in the alternative embodiment) includes,or is formed of, a magnetic material and, in particular, a magneticmaterial of the antiferromagnetic type. Suitable antiferromagneticmaterials include transition metals and their alloys. For example,suitable antiferromagnetic materials include alloys based on manganese(“Mn”), such as alloys based on iridium (“Ir”) and Mn (e.g., IrMn);alloys based on Fe and Mn (e.g., FeMn); alloys based on platinum (“Pt”)and Mn (e.g., PtMn); and alloys based on Ni and Mn (e.g., NiMn). In someinstances, the blocking temperature T_(BS) of alloys based on Ir and Mn(or based on Fe and Mn) can be in the range of about 120° C. to about220° C. or about 150° C. to about 200° C., such as about 200° C., andcan be smaller than the blocking temperature T_(BS) of alloys based onPt and Mn (or based on Ni and Mn), which can be in the range of about300° C. to about 350° C.

Referring to FIGS. 1, 2A, 2B, and 3, thermally assisted switching (TAS)technology, as applied to magnetic field sensing elements 102, providesone way of implementing a device with impedance that varies in responseto the external magnetic field 140 around an operating point configuredby the input signal 130 for use in magnetic field sensors, as explainedherein. FIG. 4 illustrates an example of a response curve (aninput-output transfer characteristic) relating an output signal 132 ofthe magnetic field sensing module 200 to an operating point configuredby the input signal 130, according to an embodiment of the invention.The below discussion of FIG. 4 illustrates the input-output transfercharacteristic of the magnetic field sensing array 100, and isapplicable to magnetic field sensing arrays 100 included in any of themagnetic field sensors described herein. In the example of FIG. 4, themagnetic field sensing array 100 includes an array of magnetic fieldsensing elements 102 with 200 parallel rows of magnetic field sensingelements 102, each row having 10 magnetic field sensing elements 102 inseries (see, for example, FIG. 10 with Np equal to 200 and Ns equal to10), and the output signal 132 of the magnetic field sensing module 200is measured across the magnetic field sensing array 100.

In one embodiment, the input signal 130 to input terminal 202 of themagnetic field sensing array 100 may flow through one or more fieldlines 112 (such as the ten field lines 1012A shown in FIG. 10) such thata magnetic field generated by the input signal is coupled to each of themagnetic field sensing elements 102. Alternatively or in addition,another input signal to input terminal 203 of the magnetic field sensingarray 100 may flow in the opposite direction through the one or morefield lines 112 such that a magnetic field generated by the anotherinput signal is also coupled to each of the magnetic field sensingelements 102. In one embodiment, the field line 112 may be positionedabout 50 nm underneath the strap 120.

When the input signal 130 is zero (e.g., zero input current assumingthat the input signal 130 to the input terminal 202 is the only input tothe magnetic field sensing array 100), the sense magnetization 144 andthe storage magnetization 146 of each of the magnetic field sensingelements 102 included in the magnetic field sensing array 100 arenaturally substantially anti-aligned (e.g., substantially antiparallel),resulting in a series impedance of 2 KΩ per magnetic field sensingelement 102 included in the magnetic field sensing array 100. When theinput signal 130 is sufficiently small (e.g., less than a value in therange from about 2 mA to about 2.25 mA per field line 112 in the exampleof FIG. 4), the sense magnetization 144 and the storage magnetization146 of each of the magnetic field sensing elements 102 included in themagnetic field sensing array 100 remain substantially antiparallel,resulting in a series impedance of about 2 KΩ per magnetic field sensingelement 102. When the input signal 130 is sufficiently large (greaterthan a value in the range from about 2.75 mA to about 3 mA per fieldline 112 in the example of FIG. 4), the sense magnetization 144 becomessubstantially aligned (e.g., substantially parallel) with the storagemagnetization 146, resulting in a series impedance of about 1 KΩ permagnetic field sensing element 102 included in the magnetic fieldsensing array 100. It is contemplated that these impedance values, andin particular the ratio between these impedance values, may be variedfor other embodiments of the magnetic field sensing elements 102 basedon forming the sense layer 104, the storage layer 106, and/or the layer108 from different choices of materials, material concentrations, and/ormaterial thicknesses.

In the example of FIG. 4, and also referring to FIG. 2B, the inputsignal 130 includes 2.5 mA DC bias current to configure the operatingpoint of the magnetic field sensing module 200. In other embodiments,the operating point may be configured by other values of the inputsignal 130, depending on factors including but not limited to theimpedance values of the magnetic field sensing elements 102 and the Npand Ns parameters of the magnetic field sensing array 100.

In addition, in one embodiment, the sense magnetizations 144 of themagnetic field sensing elements 102 may vary in response to the externalmagnetic field 140, and as a result the combined impedance of themagnetic field sensing elements 102 included in the magnetic fieldsensing array 100 may also vary in response to the external magneticfield 140. In another embodiment in which the magnetic field sensingelements 102 include a reference layer and the storage layer 106 insteadof the sense layer 104 and the storage layer 106, the storagemagnetizations 146 of the magnetic field sensing elements 102 (and thusthe combined impedance of the magnetic field sensing elements 102included in the magnetic field sensing array 100) may vary in responseto the external magnetic field 140 if the magnetic field sensingelements 102 are heated above the blocking temperature T_(BS), aspreviously described. The DC bias current 210 flows through the magneticfield sensing array 100, generating an output voltage based on thevariation of the combined impedance of the magnetic field sensingelements 102 included in the magnetic field sensing array 100. Theoutput signal 132 may be this output voltage signal, or alternativelymay be an output current signal generated based on this output voltagesignal. In the example shown in FIG. 4, the response curve relating theoutput signal 132 of the magnetic field sensing module 200 to the inputsignal 130 has a substantially linear region 410 around 2.5 mA inputcurrent per field line 112 that has a slope of about 5 Volts/mA.

The substantially linear region 410 may be formed as an average of theinput-output response curves of multiple magnetic field sensing elements102. In the example of FIG. 4, each magnetic field sensing element 102switches over a different input current range. For example, magneticfield sensing elements 102 may switch over input currents in the rangefrom about 2 mA to about 2.75 mA per field line 112 on the lower end402, and in the range from about 2.25 mA to about 3 mA per field line112 on the higher end 404 as shown in FIG. 4. To stay in the linearregion of the IV response curve, the output voltage swing resulting fromthis input current swing may be up to about 80% of the full outputvoltage range. It is contemplated that these input current ranges may bevaried across embodiments of the magnetic field sensing element 102based on forming the sense layer 104, the storage layer 106, and/or thelayer 108 from different choices of materials, material concentrations,and/or material thicknesses. For example, these input current ranges maytypically vary from those shown in FIG. 4 to an input current rangearound a DC current of about 5 mA.

In one embodiment, a magnetic field sensing array 100 included in amagnetic field sensor may be biased for small signal operation, suchthat an output 132 of the magnetic field sensing array 100 variessubstantially linearly with an external magnetic field 140 around anoperating point of the magnetic field sensing module 200 configured by aDC bias input 130 to the magnetic field sensing module 200.Alternatively or in addition, the magnetic field sensing array 100 maybe biased to substantially maximize gain of the magnetic field sensingmodule 200, such as for high-voltage applications. Alternatively, themagnetic field sensing array 100 may be biased for large signaloperation, such that the output 132 of the magnetic field sensing array100 varies substantially non-linearly with the external magnetic field140 around the operating point of the magnetic field sensing module 200configured by a DC bias input 130 to the magnetic field sensing module200. For example, the magnetic field sensing array 100 may be biased insaturation or at cut-off.

For example, there are multiple ways to set up the magnetic fieldsensing module 200, such as linear, saturated, and class C. For linearamplification, such as for class A amplification, the input DC currentcan be adjusted to an operating point (bias point) where slope of theresponse curve is the highest (e.g., where a gain of the magnetic fieldsensing module 200 is substantially maximized). In the example of FIG.4, this operating point is at about 2.5 mA input current per field line112. For maximum power efficiency, such as for class C amplification,the input DC current can be adjusted to an operating point where the DCpower associated with the DC bias current 210 in the output stage of themagnetic field sensing module 200 is at its minimum, where the operatingpoint remains within the substantially linear region 410. In the exampleof FIG. 4, this operating point is at about 2.75 mA input current. It iscontemplated that averaging of the input-output response curves of manymagnetic field sensing elements 102 (such as thousands of magnetic fieldsensing elements 102 in the example of FIG. 4) in a magnetic fieldsensing module 200 may result in increased linearity of thesubstantially linear region 410 of the magnetic field sensing module 200as compared to the input-output response curve of a single magneticfield sensing element 102. It is also contemplated that averaging of theinput-output response curves of many magnetic field sensing elements 102in each magnetic field sensing module 200 may result in greateruniformity and predictability of the class A and class C operatingpoints across the magnetic field sensing modules 200. It is alsocontemplated that averaging of the input-output response curves of manymagnetic field sensing elements 102 in each magnetic field sensingmodule 200 may result in greater robustness against failures ofindividual magnetic field sensing elements 102.

Referring to FIGS. 2B and 4, the output 132, such as a current outputand/or voltage output, of each of the magnetic field sensing modules 200is based on a direction and magnitude of the external magnetic field140. The input 130 to each magnetic field sensing module 200 can beconfigured such that the operating point of the magnetic field sensingmodule 200 remains substantially at a midpoint 406 of the substantiallylinear region 410 of the I-V response curve shown in FIG. 4, if themagnetic field sensing module 200 is not in the presence of a nonzeroexternal magnetic field 140. At this operating point, the average outputimpedance (primarily impedance) of the magnetic field sensing elements102 included in the magnetic field sensing module 200 can be about(Rmax−Rmin)/2, where Rmax is the maximum output impedance (all storagemagnetizations and sense magnetizations of the magnetic field sensingelements 102 included in the magnetic field sensing module 200 beingsubstantially anti-aligned), and where Rmin is the minimum outputimpedance (all storage magnetizations and sense magnetizations of themagnetic field sensing elements 102 included in the magnetic fieldsensing module 200 being substantially aligned). At this operatingpoint, about half of the magnetic field sensing elements 102 included inthe magnetic field sensing module 200 may be substantially aligned (withan impedance of about Rmin), and the remaining magnetic field sensingelements 102 included in the magnetic field sensing module 200 may besubstantially anti-aligned (with an impedance of about Rmax), resultingin the average output impedance of the magnetic field sensing module 200of about (Rmax−Rmin)/2. It is contemplated that each magnetic fieldsensing module 200 includes many (e.g., thousands) of magnetic fieldsensing elements 102 to increase the uniformity of average outputimpedance values across magnetic field sensing modules 200 at theoperating point.

When under the influence of the external magnetic field 140, eachmagnetic field sensing element 102 included in each of the magneticfield sensing modules 200 reacts, in that the magnetization of the senselayer 104 (see FIG. 1) of each of the magnetic field sensing elements102 can rotate to an extent dependent on the direction and magnitude ofthe external magnetic field 140. There is an antiparallel component ofthe magnetization of the sense layer 104 due to coupling with themagnetization of the storage layer 106 (see FIG. 1). As a result, whenthe external magnetic field 140 is substantially aligned with an averagestorage magnetization of the magnetic field sensing elements 102included in a particular magnetic field sensing module 200 (and oppositeto the antiparallel coupling component of the magnetization of the senselayers 104), the extent of the rotation of the sense layers 104 can beat its peak for that external magnetic field 140. In one example,assuming that the component of the external magnetic field 140 in thestorage magnetization direction 146 (see FIG. 1) is g % of the couplingcomponent of the magnetization of the sense layers 104 of the magneticfield sensing elements 102 included in the magnetic field sensing module200, the output impedance of the magnetic field sensing module 200 canchange (relative to Rmin) by about (g×(Rmax−Rmin)/Rmin) percent. Whenthe external magnetic field 140 is substantially perpendicular to theaverage storage magnetization of the magnetic field sensing module 200,the magnetic field sensing module 200 can be substantially insensitiveto the external magnetic field 140, such as at the operating point wherethe average output impedance of the magnetic field sensing module 200 isabout (Rmax−Rmin)/2. When the external magnetic field 140 issubstantially opposed to the average storage magnetization of themagnetic field sensing module 200, the output impedance of the magneticfield sensing module 200 can change (relative to Rmin) by about(g×(Rmin−Rmax)/Rmin) percent.

Referring to FIGS. 1 and 2, the output current per magnetic fieldsensing element 102 should be low enough to avoid heating the magneticfield sensing elements 102 close to the blocking temperature of thestorage layer 106 (or in other embodiments, the reference layer). In theexample of FIG. 4, the output current per magnetic field sensing element102 is set at 250 μA to prevent the stored magnetizations from switchingduring operation. In the example of FIG. 4 (with Np=200 parallel rows ofmagnetic field sensing elements 102, each row having Ns=10 magneticfield sensing elements 102 in series), the total DC output current tomaintain 250 μA per magnetic field sensing element 102 is (Np×250 μA),or 50 mA. When the DC bias current 210 is configured to be a constant 50mA applied through the output, the voltage drop is about 2.5 Volts whenall of the magnetic field sensing elements 102 are substantiallyaligned, and swings to about 5 Volts when all of the magnetic fieldsensing elements 102 are substantially anti-aligned.

Referring to FIGS. 2B and 4, the output power delivered to a load by themagnetic field sensing module 200 depends on the operating point, andimpedance matching between the output of the magnetic field sensingmodule 200 and the load. We now determine a relationship between theoutput power of the magnetic field sensing module 200 and the outputpower of an individual magnetic field sensing element 102. The outputpower of the magnetic field sensing module 200 is:Pout=Δ(Vout)×Iout/2  (1)

In this example, the magnetic field sensing module 200 has Np parallelrows of magnetic field sensing elements 102, each row having Ns magneticfield sensing elements 102 in series. The voltage drop across themagnetic field sensing module 200 is then:ΔVout=Ns×Rmtj×I _(s)  (2)where Rmtj is the impedance of each magnetic field sensing element 102with both domains substantially aligned. In this example Rmtj has avalue of approximately 1 kOhm. I_(s) is the current circulating in eachrow of Ns magnetic field sensing elements 102 in series. Then the totalcurrent circulating through the magnetic field sensing module 200 is:Iout=I _(s) ×Np  (3)

The maximum output power delivered by the magnetic field sensing module200 is:Pout=Ns×Np×Rmtj×I _(s) ²/2  (4)

The right side of this equation can be rewritten in terms of Pmtj, theoutput power delivered by a single magnetic field sensing element 102:Pout=N×Pmtj  (5)where N is the total number of magnetic field sensing elements 102 inthe magnetic field sensing module 200. This analysis indicates that thearchitecture of the magnetic field sensing module 200 may be highlyscalable, as the higher the number of interconnected magnetic fieldsensing elements 102, the higher the output power of the magnetic fieldsensing module 200 may be. This analysis also indicates that the outputpower of the magnetic field sensing module 200 may not be dependent onwhether the magnetic field sensing elements 102 are connected in seriesor in parallel. For example, a magnetic field sensing module 200including 50,000 magnetic field sensing elements 102 has a Pout of 10 mWfor various possible example configurations:

Configuration 1: Np=2,500, Ns=20: ΔVout=0.4V Iout=50 mA Pout=10 mW

Configuration 2: Np=1,000, Ns=50: ΔVout=1.0V Iout=20 mA Pout=10 mW

Configuration 3: Np=500, Ns=100: ΔVout=2.0V Iout=10 mA Pout=10 mW

For configuration 3, for a value of Pin, the power in, of 0.5 μW, thePout in the linear range may be at least 5 mW, so the resulting gain inpower may be 5,000.

As can be seen from the above example, and referring to FIG. 2B, the DCbias current 210 and the peak-to-peak voltage of the output signal 132for a given maximum output power of the magnetic field sensing module200 are dependent on the number of parallel rows of magnetic fieldsensing elements 102, and the number of magnetic field sensing elements102 in series in each row. The DC bias current 210 and the peak-to-peakvoltage of the output signal 132 for a given maximum output power of themagnetic field sensing module 200 are therefore dependent on thecombined impedance of the magnetic field sensing elements 102 includedin the magnetic field sensing module 200.

The performance of the magnetic field sensing elements 102 can becharacterized in terms of tunnel magnetoiresistance (TMR). TMR can beexpressed as:TMR=((Ranti-parallel)−(Rparallel))/(Rparallel)  (7)For an Rparallel of 1 kOhm and an Ranti-parallel of 2 kOhm, the TMR is100%, which may yield a power added efficiency that is below 50% classC. A TMR of 200% may yield a higher power added efficiency of 66%, and aTMR of 1000% may yield 90%. These higher TMR values may allow themagnetic field sensing module 200 to operate with a lower static DC biascurrent, minimizing power losses. Increasing TMR may also increaselinearity.

Referring to FIGS. 1 and 3, the storage layer 106 may be configuredthrough a configuration operation. This configuration operation mayoccur during operation of the magnetic field sensing module 200. In oneembodiment, during a programming cycle, a relatively small current isapplied through the magnetic field sensing element 102 to heat thepinning layer 910 by Ohmic effect. When a temperature of the pinninglayer 910 is above a threshold temperature, the direction of the storagemagnetization 146 is unpinned, thereby allowing the storagemagnetization 146 to be programmed by applying a current through thefield line 112 that is magnetically connected to the cell. The storagemagnetization 146 can be configured in a first direction by applying thecurrent in one particular direction, and can be configured in a seconddirection opposite to the first direction by applying the current in anopposite direction. After programming, the magnetic field sensingelement 102 is cooled below the threshold temperature, thereby pinningthe storage magnetization 146 in the programmed direction.

In addition, a magnetization of the storage layer 106 (or in anotherembodiment, the reference layer) may be pre-configured, such as in thefactory. The storage magnetization 146 may be pre-configured by at leastone of an internal magnetic field generated by a field line 112associated with the magnetic field sensing module 200, an externalmagnetic field, an internal heating mechanism (such as differential orlocalized heating, such as using a bit line associated with one or moreof the magnetic field sensing elements 102 included in the magneticfield sensing module 200, described below), and an external heatingmechanism. Various combinations of the above may be used. For example,pre-configuration may be performed using an internal magnetic field andinternal heating may be used. Alternatively or in addition,pre-configuration may be performed using an external magnetic field andinternal heating may be used. Alternatively or in addition,pre-configuration may be performed using an external magnetic field anda combination of external heating and internal heating. Alternatively orin addition, pre-configuration may be performed using an internalmagnetic field and a combination of external heating and internalheating. Alternatively or in addition, pre-configuration may beperformed using a combination of an external magnetic field and aninternal magnetic field, and a combination of external heating andinternal heating.

Still referring to FIGS. 1 and 3, the magnetic field sensing array 100may also include a set of traces (or strip conductors) to provideprogramming functions. Specifically, a bit line 916 is electricallyconnected to the magnetic field sensing element 102 on the side of thesense layer 104 (or, in an alternative embodiment, the reference layer)and is substantially orthogonal to the field line 112, which is disposedbelow and magnetically connected to the magnetic field sensing element102 on the side of the storage layer 106. The bit line 916 may includeat least part of the output line 116 of FIG. 1, or may correspond to theoutput line 116 of FIG. 1. The magnetic field sensing array 100 mayfurther include a transistor 918, which is electrically connected,through the strap 120, to the magnetic field sensing element 102 on theside of the storage layer 106. The transistor 918 is switchable betweena blocked mode (OFF) and a conducting mode (ON), thereby allowing theflow of a current through the magnetic field sensing element 102. Otherimplementations of the magnetic field sensing array 100 arecontemplated. For example, the relative orientation of the bit line 916and the field line 112 can be varied from that illustrated in FIG. 4. Asanother example, the relative positioning of the bit line 916 and thefield line 112 can be reversed, with the field line 112 disposed abovethe bit line 916.

Referring to FIG. 3, during a TAS-type programming cycle, the magneticfield sensing element 102 is heated by applying a heating currentthrough the magnetic field sensing element 102 via the bit line 916,with the transistor 918 in a conducting mode. The magnetic field sensingelement 102 is heated to a temperature above the blocking or thresholdtemperature T_(BS) of the pinning layer 910, such that a magnetizationof the storage layer 106 is unpinned. (In the alternative embodiment,the magnetic field sensing element 102 is heated to a temperature abovethe blocking or threshold temperature T_(BS) of the pinning layer 910but below the blocking or threshold temperature T_(BR) of the additionalpinning layer, such that a magnetization of the storage layer 106 isunpinned but the magnetization of the reference layer remains fixed.)Simultaneously or after a short time delay, the field line 112 isactivated to induce a write magnetic field to switch the storagemagnetization from an initial direction to another direction.Specifically, a write current is applied through the field line 112 toinduce the write magnetic field to switch the storage magnetizationdirection, according to the direction of the write current. Because thestorage magnetization direction can be aligned according to the writemagnetic field, the storage magnetization direction can be switchedbetween multiple directions according to a programming encoding scheme.One possible encoding scheme is implemented with a pair of directionsthat are displaced by about 180°, such that a “0” is assigned to one ofthe pair of directions, and a “1” is assigned to another one of the pairof directions.

Once the storage magnetization is switched to a programmed direction,the transistor 918 is switched to a blocked mode to inhibit current flowthrough the magnetic field sensing element 102, thereby cooling themagnetic field sensing element 102. The write magnetic field can bemaintained during cooling of the magnetic field sensing element 102, andcan be deactivated once the magnetic field sensing element 102 hascooled below the blocking temperature T_(BS) of the pinning layer 910.Because the storage magnetization direction is pinned by the exchangebias of the pinning layer 910, its orientation remains stable so as toretain the stored magnetization direction.

Other implementations of programming cycles are contemplated. Forexample, the magnetic field sensing element 102 can be implemented withan anisotropic shape having a relatively high aspect ratio, such asabout 1.5 or more. In such an anisotropic-shaped implementation of themagnetic field sensing element 102, the storage magnetization directioncan be switched and can remain stable, without requiring the pinninglayer 910. As another example, a programming cycle can be carried out byapplying a write current through the magnetic field sensing element 102via the bit line 916, using the so-called spin transfer torque (“STT”)effect. In such a STT-type programming cycle, the write current canbecome spin polarized by passing through a polarizing magnetic layer(not illustrated) or through the sense layer 104, and a magnetization ofthe storage layer 106 can be switched according to a spin-polarizedorientation of the write current. Switching of the storage layermagnetization with the spin-polarized write current also can be combinedwith a TAS-type programming cycle, such as by heating the magnetic fieldsensing element 102 above the blocking temperature T_(BS) and thenapplying the spin-polarized write current through the magnetic fieldsensing element 102.

FIG. 5 illustrates a logical block diagram of a magnetic field sensingdevice 500 showing one of multiple magnetic field sensing modules 200included in the magnetic field sensing device 500, according to anembodiment of the invention. FIG. 6 illustrates a top view of a magneticfield sensing device 600 including a configuration of magnetic fieldsensing modules 200, according to an embodiment of the invention.

The magnetic field sensing device 500 includes multiple magnetic fieldsensing modules 200. The magnetic field sensing module 200 may includethe magnetic field sensing array 100 (see FIG. 1), or other embodimentsof magnetic field sensing arrays previously described. The magneticfield sensing device 600 has the logical structure of the magnetic fieldsensing device 500. The magnetic field sensing module 200 may include anarray of Np rows of magnetic field sensing elements 102 in parallel,with Ns magnetic field sensing elements 102 in series per row (see FIG.10).

Referring to FIGS. 1 and 6, an average storage magnetization of each ofthe magnetic field sensing modules 200 (details of the magnetic fieldsensing modules not shown in FIG. 6) corresponds to a magnetizationdirection of an average of storage magnetizations 146 (magnetizations ofthe storage layers 106) of the magnetic field sensing elements 102included in the each of the magnetic field sensing modules 200. It iscontemplated that the magnetic field sensing device 600 is configuredsuch that the magnetic field sensing elements 102 have substantially thesame storage magnetizations resulting from magnetic fields generated bycurrent flowing through one or more field lines (such as field lines612), within the limits of manufacturing tolerances (such as of themagnetic field sensing elements 102) and non-uniformity in the magneticfields generated by the field lines in the regions in which the magneticfield sensing elements 102 are located.

In one embodiment, the magnetic field sensing device 600 may includemultiple magnetic field sensing modules 200 connected through a singlefield line. Alternatively, the magnetic field sensing modules 200 may beconnected through multiple field lines, such as multiple field lines inparallel. The field line(s) 612 shown in FIG. 6 may represent a singlefield line, or alternatively may represent multiple field lines inparallel. The average storage magnetization direction of each of themagnetic field sensing modules 200 is unique so that the average storagemagnetization direction of each of the magnetic field sensing modules200 is oriented differently relative to the external magnetic field 140(see FIG. 1).

In the embodiment of FIG. 6, the magnetic field sensing modules 200 arespaced such that magnetic field sensing modules 200 having oppositeaverage storage magnetization directions are disposed adjacent to(neighboring) each other. Alternatively, in another embodiment, magneticfield sensing modules 200 having opposite average storage magnetizationdirections may be disposed opposite to each other. The average storagemagnetization directions of the magnetic field sensing modules 200included in the magnetic field sensing device 600 are substantiallyequally spaced by an angle of about 360 degrees divided by 8 (the numberof magnetic field sensing modules 200), or about 45 degrees.Specifically, in the embodiment of FIG. 6, the magnetic field sensingmodules 200A-200H are located at angles of about 0°, about 45°, about90°, about 135°, about 0°, about 45°, about 90°, and about 135°,respectively, relative to axis 602 extending from the magnetic fieldsensing module 200A. However, because current flows through the fieldline 612 in opposite directions for adjacent pairs of magnetic fieldsensing modules 200 (such as magnetic field sensing modules 200A and200E), the average storage magnetizations of the magnetic field sensingmodules 200B-200H rotate by about 45°, about 90°, about 135°, about180°, about 225°, about 270°, and about 315°, respectively, relative tothe average storage magnetization of the magnetic field sensing module200A.

It is contemplated that more or fewer magnetic field sensing modules 200than 8 may be included in the magnetic field sensing device 600. Forexample, if N magnetic field sensing modules 200 are included in themagnetic field sensing device 600, then the average storagemagnetization directions of the N magnetic field sensing modules 200 canbe substantially equally spaced by an angle of 360 degrees divided by N.It is also contemplated that in other embodiments, the magnetic fieldsensing modules 200 may be arranged in other ways. For example, thestorage magnetization directions of the magnetic field sensing modules200 may not be substantially equally spaced. Also, the magnetic fieldsensing modules 200 may be spaced such that magnetic field sensingmodules 200 having opposite average storage magnetization directions areneither disposed adjacent to (neighboring) each other, nor substantiallyopposite to each other.

FIGS. 7 and 8 illustrate the storage magnetization directions 146 andthe sense magnetization directions 144 of magnetic field sensingelements 102 in the presence of the external magnetic field 140,according to an embodiment of the invention. In FIG. 7, a direction 700of the external magnetic field 140 is substantially aligned with thestorage magnetization directions 146 of the magnetic field sensingelements 102 included in the magnetic field sensing module 200 (see FIG.5). In this case, the magnetization of the storage layer 106 (seeFIG. 1) is effectively increased, which increases the substantiallyanti-parallel coupling magnetization of the sense layer 104 (see FIG.1). So in this case, the percentage of the magnetic field sensingelements 102 for which the storage magnetization direction 146 and thesense magnetization direction 144 are substantially anti-parallel isgreater than 50% at the operating point 406 (see FIG. 4), and thepercentage of the magnetic field sensing elements 102 for which thestorage magnetization direction 146 and the sense magnetizationdirection 144 are substantially parallel is less than 50% at theoperating point 406. This results in an increase in the output impedanceof the magnetic field sensing module 200. In one embodiment, thisresults in an increase in the output signal 132, which can be a voltagemeasured across the magnetic field sensing module 200.

Conversely, for a direction 702 of the external magnetic field 140 thatis substantially anti-aligned with the storage magnetization directions146 of the magnetic field sensing elements 102 included in the magneticfield sensing module 200, the magnetization of the storage layer 106(see FIG. 1) is effectively decreased. In this case, the percentage ofthe magnetic field sensing elements 102 for which the storagemagnetization direction 146 and the sense magnetization direction 144are substantially anti-parallel is less than 50% at the operating point406 (see FIG. 4), and the percentage of the magnetic field sensingelements 102 for which the storage magnetization direction 146 and thesense magnetization direction 144 are substantially parallel is greaterthan 50% at the operating point 406. This results in a decrease in theoutput impedance of the magnetic field sensing module 200. In oneembodiment, this results in a decrease in the output signal 132, whichcan be a voltage measured across the magnetic field sensing module 200.

Referring to FIGS. 5 and 6, pairs of magnetic field sensing modules 200(200A and 200E; 200B and 200F; 200C and 200G; 200D and 200H) havesubstantially opposed storage magnetization directions 146 (see FIG. 1).To enhance detection of the external magnetic field 140, it isadvantageous to detect a differential signal that is the differencebetween the output signals 132 of these pairs of magnetic field sensingmodules 200. For example, as shown in the examples of FIG. 7, amagnitude of this differential signal may be increased relative to theoutput signals 132. This can be to enhance detection of the externalmagnetic field 140, and can be to suppress common mode noise (offset).Also as shown in the examples of FIG. 7, the magnitude of thisdifferential signal may be maximized for the pair of magnetic fieldsensing modules 200 for which the direction of the external magneticfield 140 is substantially aligned with the storage magnetizationdirections 146 of the magnetic field sensing elements 102 included inone of the pair (and therefore substantially anti-aligned with the otherof the pair). The sign of the differential signal is different for thetwo examples of FIG. 7.

In FIG. 8, for directions 800 and 802 of the external magnetic field 140that are substantially perpendicular to the storage magnetizationdirections 146 of the magnetic field sensing elements 102 included inthe magnetic field sensing module 200, the magnetization of the senselayer 104 (see FIG. 1) is slightly rotated. For both of the directions800 and 802, the external magnetic field 140 may slightly decrease theadditional magnetic field needed to switch the magnetization of thesense layer 104 from substantially anti-parallel to substantiallyparallel to the storage magnetization direction 146. In this case, thepercentage of the magnetic field sensing elements 102 for which thestorage magnetization direction 146 and the sense magnetizationdirection 144 are substantially anti-parallel may be less than 50% atthe operating point 406 (see FIG. 4), and the percentage of the magneticfield sensing elements 102 for which the storage magnetization direction146 and the sense magnetization direction 144 are substantially parallelmay be greater than 50% at the operating point 406. This results in adecrease in the output impedance of the magnetic field sensing module200. In one embodiment, this results in a decrease in the output signal132, which can be a voltage measured across the magnetic field sensingmodule 200.

As shown in the examples of FIG. 8, the magnitude of a differentialsignal between a pair of magnetic field sensing modules 200 (see FIG. 5)for which the external magnetic field 140 is substantially perpendicularto the storage magnetization directions 146 (see FIG. 1) of the magneticfield sensing elements 102 included in the magnetic field sensingmodules 200 may be approximately zero. This is because the effect of theEarth's magnetic field in the directions 800 and 802 on the outputimpedances of the pair of magnetic field sensing modules 200 may besubstantially the same.

Referring to FIG. 5, the magnetic field sensing device 500 includes amagnetic field determination module 502 configured to determine aparameter of each of the magnetic field sensing modules 200 included inthe magnetic field sensing device 500. This parameter varies based onimpedances of the magnetic field sensing elements 102 included in eachof the magnetic field sensing modules 200. In one embodiment, thisparameter is an output impedance. In another embodiment, this parameteris a voltage and/or a current. It is contemplated that this parameter isnot limited to these types, but instead may be of any type measured bythe magnetic field determination module 502 that varies in a predictablemanner based on the output impedance of the magnetic field sensingmodules 200.

Referring to FIG. 5, we now present an example of output voltagemeasurements of each of the magnetic field sensing modules 200 includedin the magnetic field sensing device 500 by the magnetic fielddetermination module 502. The parameters used in this example are below:

-   -   Size of MTJ: 90 nm    -   TMR=100%    -   Rmin=4KΩ; Rav=6KΩ; Rmax=8KΩ    -   For each of 8 magnetic field sensing modules (MFSM) 200:        -   Np=200; Ns=10; N=2,000; Rmin_mfsm=200Ω; Rav_mfsm=300Ω;            Rmax_mfsm=400Ω (Rmin_mfsm, Rav_mfsm, and Rmax_mfsm are for            200 parallel rows of magnetic field sensing elements 102,            with 10 magnetic field sensing elements 102 in series in            each row)        -   Input stage: Iin=25 mA (we assume 5 field lines in parallel            per magnetic field sensing module 200, 5 mA per field line;            each field line is across, and thereby magnetically            connected to, two magnetic field sensing modules 200 in            series)        -   Input impedance: estimated around 25Ω; Vin=0.625V        -   Output stage: Vcc=3V; Icc (DC bias current 210)=10 mA; Is            (DC current per row of magnetic field sensing elements            102)=50 μA    -   Coupling magnetic field=50 Oe; external magnetic field: 0.5 Oe        or 1%    -   ΔV for 1% effect: 20 mV

Table 1 shows the output voltage measurements by the magnetic fielddetermination module 502 for the 8 magnetic field sensing modules 200 inthe above example. These output voltage measurements (ΔV) are thedifference between the actual output voltage across each of the magneticfield sensing modules 200 and the bias voltage Vcc of the output stage(3 Volts in this example). Differential measurements of ΔV across pairsof magnetic field sensing modules (such as magnetic field sensingmodules 1 and 5 in Table 1 below) have twice the magnitude of themeasurements shown in Table 1. The magnetic field sensing module 1 (inTable 1 below) has a storage magnetization direction 146 (see FIG. 1)that is substantially aligned with the external magnetic field 140. Themagnetic field sensing modules 2 through 8 (in Table 1 below) havestorage magnetization directions 146 that are at x degrees relative tothe external magnetic field 140, as shown in Table 1.

TABLE 1 Example of voltage measurements of 8 magnetic field sensingmodules 200 by the magnetic field determination module 502 1 2 3 4 5 6 78 Angle (x°) 0 45 90 135 180 225 270 315 ΔV (mV) 20 14 0 −14 −20 −14 014

In one embodiment, it is contemplated that a magnetic field sensingdevice 500 including the 8 magnetic field sensing modules 200 can beimplemented in an integrated circuit having a die size of 0.125 squaremillimeters.

Referring to FIG. 5, the magnetic field sensing device 500 has input 130and output 132. The input 130 may be a DC bias current and/or voltagefor which the magnetic field sensing modules 200 are substantially atthe operating point 406 (see FIG. 4). In one embodiment, the input 130does not include an additional AC signal. Alternatively, the input 130may include an additional AC or RF signal. A version of this additionalAC signal would appear in measurements of the output 132 by the magneticfield determination module 502.

The magnetic field sensing device 500 also includes a control module504. The control module 504 may measure the output impedance of eachmagnetic field sensing module 200 (or alternatively may measure theoutput 132 and obtain the output impedance based on the output 132). Thecontrol module 504 may adjust the input signal 130 such that themagnetic field sensing modules 200 are each set at an operating point atthe midpoint 406 of the substantially linear region 410 of the I-Vresponse curve (see FIG. 4). At the midpoint 406, the device sensitivitymay be at its maximum. In one embodiment, the control module 504 alsocompensates for temperature variations and other effects that may causethe operating point to drift from the midpoint 406. The control module504 may be implemented through a complementary metal oxide semiconductor(CMOS) process.

In one embodiment, the control module 504 may control a switch 508 (suchas a transistor) that can turn the DC bias current 210 to the magneticfield sensing array 100 on or off. Power can be saved by turning on theDC bias current 210 only when needed for the magnetic field sensingdevice 500 to measure the direction of the external magnetic field 140(see FIG. 2B). In the example of Table 1, for each of the magnetic fieldsensing modules 200, the power consumption is based on the followingparameters:

-   -   Output: Vcc=3V Icc (DC bias current 210)=20 mA for 20 ns    -   Input: Vin=0.625V Iin (input signal 130)=25 mA for 20 ns

In the example of Table 1, the DC bias current 210 is applied for 20nanoseconds, during which the magnetic field determination module 502can perform measurements of the output 132. Similarly, the input signal130 can be applied for 20 nanoseconds. The control module 504 may turnthe input signal 130 on and off in a similar manner to that shown inFIG. 5 for the DC bias current 210.

In one embodiment, the magnetic field determination module 502 maydetermine the input impedance, voltage, and/or current of each magneticfield sensing module 200 (or alternatively may measure the input 130 andobtain the input impedance, voltage, and/or current based on the input130). The magnetic field determination module 502 may extract minimumand maximum values of the input impedance, voltage, and/or current ofeach magnetic field sensing module 200.

From these measurements, the magnetic field determination module 502 canalso determine the angular orientation of the magnetic field sensingdevice 500 relative to the external magnetic field 140 based on theparameter (such as the output impedance, output voltage, or outputcurrent) of each of the magnetic field sensing modules 200. The magneticfield determination module 502 may be configured to determine theangular orientation of the magnetic field sensing device 500 relative tothe external magnetic field 140 in three dimensions based on Hall effectvertical axis sensing. In one embodiment, the magnetic fielddetermination module 502 may estimate this angular orientation based onthese measurements, such as through interpolation or other algorithms.

The magnetic field sensing device 500 can operate with magnetic fieldsensing elements 102 that are not linear due to hysteresis. In oneembodiment, the control logic 504 increases the input 130 regularly(such as periodically) to measure the output impedance of each magneticfield sensing module 200 at the midpoint 506 (see FIG. 5). Since themeasurements are occurring while the input 130 is increasing, hysteresisthat results when the input 130 is decreasing does not affect themagnetic field sensing device 500. Alternatively, the control logic 504can decrease the input 130 regularly to measure the output impedance ofeach magnetic field sensing module 200 at the midpoint 406 (see FIG. 4).In this embodiment, since the measurements are occurring while the input130 is decreasing, hysteresis that results when the input 130 isincreasing does not affect the magnetic field sensing device 500.

FIG. 9 illustrates a top view of the portion 601 of the magnetic fieldsensing device 600 of FIG. 6 including a top view of the pair ofmagnetic field sensing modules 200A and 200E included in the portion 601of the magnetic field sensing device 600, according to an embodiment ofthe invention. FIG. 10 illustrates an expanded top view of the pair ofmagnetic field sensing modules 200A and 200E of FIG. 9, according to anembodiment of the invention. Each of the magnetic field sensing modules200A-200H includes a corresponding magnetic field sensing array100A-100H (see FIG. 6) that includes Np rows 902A-902N of magnetic fieldsensing elements 102 in parallel, and Ns magnetic sensing elements 102per row 902 connected in series.

In one embodiment, the field line 612 may be a single field line.Alternatively, the field line 612 may represent multiple field lines1012 in parallel. Each of the multiple field lines 1012 has an impedancethat may include a resistive component (corresponding to impedance) anda reactive component (corresponding to an inductance and/or acapacitance). It may be advantageous to provide multiple field lines1012 in parallel to reduce the input impedance of the magnetic fieldsensing module 200. Multiple field lines 1012 in parallel have a lowerimpedance, which can reduce the input power dissipation per magneticfield sensing element 102. Multiple field lines 1012 in parallel mayalso increase the effectiveness of cladding adjacent to the field lines1012 (for focusing the magnetic field generated by the field lines 1012so that magnetic coupling to the magnetic field sensing elements 102 isincreased) as compared to a single wider field line 612 described withreference to FIG. 6. In one embodiment, each of the multiple field lines1012 is magnetically connected to one of the magnetic field sensingelements 102 in each row 902. Alternatively, one or more of the multiplefield lines 102 may be magnetically connected to multiple adjacent onesof the magnetic field sensing elements 102 in each row 902.

In one embodiment, each magnetic field sensing array 100 of magneticsensing elements 102 included in the magnetic field sensing device 600may be magnetically connected to the field line 612. The field line 612may be curved and/or serpentine (shown in FIG. 6). In this embodiment,the input current 130 (see FIG. 2) flowing through the field line 612flows in a first direction relative to the magnetic field sensingelements 102 included in the magnetic field sensing module 200A, and ina second direction substantially opposite to the first directionrelative to the magnetic field sensing elements 102 included in themagnetic field sensing module 200E. In this embodiment, the same is truefor the pairs of magnetic field sensing modules (200B, 200F), (200C,200G), and (200D, 200H). As a result, a direction of the storagemagnetization 146 of the magnetic field sensing elements 102 included inthe magnetic field sensing module 200A resulting from the input current130 is substantially opposite to a direction of the storagemagnetization 146 of the magnetic field sensing elements 102 included inthe magnetic field sensing module 200E resulting from the input current130. In this way, the serpentine characteristic of the field line 612and the field lines 1012 facilitates differential detection, aspreviously described with reference to FIG. 7.

In one embodiment, referring to FIG. 2B, the DC bias current 210 of themagnetic field sensing module 200A flows through the magnetic fieldsensing module 200A from a pad 1020 to a ground pad 903, and the DC biascurrent 210 of the magnetic field sensing module 200E flows through themagnetic field sensing module 200E from a pad 1022 to the ground pad903. The differential voltage output across the magnetic field sensingmodules 200A and 200E can be measured as the difference between thevoltage at the pad 1020 and the voltage at the pad 1022.

There are a number of advantages of the magnetic field sensing array 100as used in the embodiment of FIGS. 9 and 10. The DC bias current 210(see FIG. 2B) is divided among the Np rows 902 connected in parallel, soNp can be configured such that the magnetic field sensing elements 102avoid, for example, the breakdown voltage of MTJ's. A representativevoltage threshold for MTJ's to avoid breakdown is approximately 0.5Volts per MTJ, though this voltage threshold can vary based on, forexample, different choices of materials, material concentrations, and/ormaterial thicknesses. A corresponding current threshold for MTJ's havingRmin of 1 KΩ and Rmax of 2 KΩ is 250 μA. Given these voltage/currentthresholds, the number Ns of magnetic field sensing elements 102 per row902 connected in series can be configured so that the magnetic fieldsensing device 600 meets output voltage/current requirements. Forexample, for Ns=10, the output voltage and current per magnetic fieldsensing module 200 are 2.5 V to 5 V (for Rmin of 1 KΩ and Rmax of 2 KΩ,respectively) and 50 mA, respectively.

In addition, an increased number Np of rows 902 connected in parallelallows for increased robustness of the magnetic field sensing arrays 100against failures of one or more magnetic field sensing elements 102included in the magnetic field sensing arrays 100, as the larger thenumber Np of rows 902 in parallel for a given value of Ns, the less theeffect (typically) on the overall impedance of the magnetic fieldsensing array 100 due to failure of the one or more magnetic fieldsensing elements 102. For example, if there are no MTJ failures, theimpedance of the magnetic field sensing array 100 is Rmtj*Ns/Np. Ifthere is a single MTJ failure that renders one of the rows 902 an opencircuit, then the impedance of the magnetic field sensing array 100becomes Rmtj*Ns/(Np−1). For Np=200, the difference between theseimpedance values is only approximately 0.5%.

Also, as previously described, the output power of the magnetic fieldsensing array 100 increases with the total number of magnetic fieldsensing elements 102 included in the magnetic field sensing array 100.The product Ns*Np can thereby be configured so that the magnetic fieldsensing device 600 meets output power requirements.

An example of the response curve relating an output signal of themagnetic field sensing modules 200 in the embodiment of FIGS. 9 and 10to an input signal of the magnetic field sensing modules 200 in theembodiment FIGS. 9 and 10 is shown in FIG. 4, according to an embodimentof the invention.

FIG. 11 illustrates a perspective view of a portion 1100 of one of thepair of magnetic field sensing modules 200A and 200E of FIG. 10,according to an embodiment of the invention. In one embodiment, theportion 1100 includes, for a single row 902 included in one of themagnetic field sensing modules 200 of FIG. 10, the pads 1020 and 903,the magnetic field sensing elements 102, and the associated conductivelayers electrically connected and magnetically connected to the magneticfield sensing elements 102. The portion 1100 includes magnetic fieldsensing elements 1110A-1110N (in one embodiment, corresponding to themagnetic field sensing elements 102 of FIG. 10, which can be MTJs), afirst conductive layer 1101 including conductive interconnects1102A-1102N that are each connected to a corresponding one or a pair ofthe magnetic field sensing elements 1110, a second conductive layer 1103including straps 1104A-1104N that are each connected to a correspondingpair of the magnetic field sensing elements 1110, and a third conductivelayer 1105 including field lines 1106A-1106N (in one embodiment,corresponding to the field lines 1012 of FIG. 10). Each of the fieldlines 1106 is magnetically coupled to a corresponding one of themagnetic field sensing elements 1110. In one embodiment, the portion1100 includes a fourth conductive layer 1120 that includes sections1122A-1122N (in one embodiment, corresponding to one or more of the pads1020, 1030, and 903 of FIG. 10). The first conductive layer 1101 and thethird conductive layer 1105 may be formed of Cu or other materials knownto one of ordinary skill in the art. The second conductive layer 1103may be formed of tantalum nitride (TaN) or other materials known to oneof ordinary skill in the art. The fourth conductive layer 1120 may beformed of aluminum (Al) or other materials known to one of ordinaryskill in the art. The fourth conductive layer is optional, as in certainapplications (such as for integrated sensors) the magnetic field sensingmodules 200 of FIG. 10 may be directly connected to other circuitry on achip.

FIG. 12 illustrates a top view of the portion 601 of the magnetic fieldsensing device 600 of FIG. 6 including a top view of the pair ofmagnetic field sensing modules 200A and 200E included in the portion 601of the magnetic field sensing device 600, according to an embodiment ofthe invention. FIG. 13 illustrates an expanded top view of the pair ofmagnetic field sensing modules 200A and 200E of FIG. 12, according to anembodiment of the invention. Each of the magnetic field sensing modules200A-200H includes a corresponding magnetic field sensing array100A-100H (see FIG. 6) that includes G subarrays 1201A-1201N of magneticfield sensing elements 102. Each of the G subarrays 1201 includes Np_subrows 1202A-1202N of magnetic field sensing elements 102 in parallel, andNs_sub magnetic sensing elements 102 per row 1202 connected in series.

As previously described with reference to FIGS. 9 and 10, the field line612 may be a single field line. Alternatively, the field line 612 mayrepresent multiple field lines 1012 in parallel. Also as previouslydescribed with reference to FIGS. 9 and 10, the serpentinecharacteristic of the field line 612 and the field lines 1012facilitates differential detection. In one embodiment, referring to FIG.2B, the DC bias current 210 of the magnetic field sensing module 200Aflows through the magnetic field sensing module 200A from a pad 1310A toa ground pad 1203, and the DC bias current 210 of the magnetic fieldsensing module 200E flows through the magnetic field sensing module 200Efrom a pad 1320 to the ground pad 1203. The differential voltage outputacross the magnetic field sensing modules 200A and 200E can be measuredas the difference between the voltage at the pad 1310A and the voltageat the pad 1320.

There are a number of advantages of the magnetic field sensing array 100(including subarrays 1201) as used in the embodiment of FIGS. 12 and 13for higher voltage applications such as automotive applications (in oneexample, a 20 Volts to 40 Volts output voltage requirement, though therange of voltages for these applications is not restricted to thisrange). As output voltage requirements increase, Ns tends to increaseand Np tends to decrease in the embodiment of FIGS. 9 and 10. This leadsto an increase in the Ns field lines 1012 needed in the embodiment ofFIGS. 9 and 10, which leads to an increase in the DC bias current 210(see FIG. 2) needed, as the DC bias current 210 is divided between theNs field lines 1012. One benefit of partitioning the magnetic fieldsensing array 100 into the G subarrays 1201 is that the number of fieldlines can be reduced by a factor of G. In the embodiment of FIGS. 12 and13, the number G of subarrays 1201 can be configured such that Ns_sub(equal to Ns/G) is less than Np_sub (equal to Np). Through use of thesubarrays 1201, the number of field lines 1012 can therefore be reducedfrom Ns (in the embodiment of FIGS. 9 and 10) to Ns_sub, which is Ns/G,resulting in significantly reduced output current and powerrequirements. For example, for Ns_sub=4, Np_sub=40, and G=20, the outputvoltage and current per magnetic field sensing module 200 are 20 V to 40V (for Rmin of 1 KΩ and Rmax of 2 KΩ, respectively) and 10 mA,respectively.

In addition, as output voltage requirements increase, the increase in Nsand the decrease in Np in the embodiment of FIGS. 9 and 10 tends toreduce robustness of the magnetic field sensing arrays 100 againstfailures of one or more magnetic field sensing elements 102 included inthe magnetic field sensing arrays 100. For example, in the embodiment ofFIGS. 9 and 10, for Ns=80 and Np=40, if there are no MTJ failures, theimpedance of the magnetic field sensing array 100 is Rmtj*Ns/Np=Rmtj*2.If there is a single MTJ failure that renders one of the rows 902 anopen circuit, then the impedance of the magnetic field sensing array 100becomes Rmtj*Ns/(Np−1)=Rmtj*80/39. The difference between theseimpedance values is approximately 2.5%. The partitioning of the magneticfield sensing array 100 into the G subarrays 1201 is a way to furtherincrease the robustness of the magnetic field sensing arrays 100 againstfailures of one or more magnetic field sensing elements 102 included inthe magnetic field sensing arrays 100, even for output voltagerequirements in, for example, the 20 V to 40 V range. If there are noMTJ failures, the impedance of the magnetic field sensing array 100 isRmtj*G*Ns_sub/Np_sub=Rmtj*2. If there is a single MTJ failure thatrenders one of the rows 1202 an open circuit, then the impedance of themagnetic field sensing array 100 becomesRmtj*((G−1)*Ns_sub/Np_sub+Ns_sub/(Np_sub−1))=Rmtj*2.0026. The differencebetween these impedance values is approximately 0.13%, approximately afactor of 20 lower than in the embodiment of FIGS. 9 and 10 for thishigher voltage application.

Also, as previously described, the output power of the magnetic fieldsensing array 100 increases with the total number of magnetic fieldsensing elements 102 included in the magnetic field sensing array 100.The product G*Ns_sub*Np_sub can thereby be configured so that themagnetic field sensing device 600 meets output power requirements.

FIG. 14 illustrates an example of a response curve relating an outputsignal of the magnetic field sensing modules 200 in the embodiment ofFIGS. 12 and 13 to an input signal to the magnetic field sensing modules200 in the embodiment of FIGS. 12 and 13, according to an embodiment ofthe invention. The description of FIG. 14 is in many respects similar toFIG. 4, so only portions that are different are stated here. FIG. 14 isfor the structure of the magnetic field sensing modules 200 in theembodiment of FIGS. 12 and 13, which has Ns_sub=4, Np_sub=40, and G=20.In this example, the input DC current 130 (see FIG. 2B) is 10 mA(divided among 4 field lines 1012, as shown in FIG. 13), and the outputDC current 132 is 10 mA, as previously described with reference to FIGS.12 and 13. In this example, the output voltage is in the range from 20 Vto 40 V, as previously described with reference to FIGS. 12 and 13.

FIG. 11 also illustrates a perspective view of a portion 1100 of one ofthe pair of magnetic field sensing modules 200A and 200E of FIG. 13,according to an embodiment of the invention. In one embodiment, theportion 1100 includes, for a single row 1202 included in one of themagnetic field sensing modules 200 of FIG. 13, the pads (sections) 1310Aand 1310B, the magnetic field sensing elements 102, and the associatedconductive layers electrically connected and magnetically connected tothe magnetic field sensing elements 102. The portion 1100 includesmagnetic field sensing elements 1110A-1110N (in one embodiment,corresponding to the magnetic field sensing elements 102 of FIG. 13,which can be MTJs), a first conductive layer 1101 including conductiveinterconnects 1102A-1102N that are each connected to a corresponding oneor a pair of the magnetic field sensing elements 1110, a secondconductive layer 1103 including straps 1104A-1104N that are eachconnected to a corresponding pair of the magnetic field sensing elements1110, and a third conductive layer 1105 including field lines1106A-1106N (in one embodiment, corresponding to the field lines 1012 ofFIG. 13). Each of the field lines 1106 is magnetically coupled to acorresponding one of the magnetic field sensing elements 1110. In oneembodiment, the portion 1100 includes a fourth conductive layer 1120that may include sections 1310A-1310N (in one embodiment, including thepads 1310A and 1310B of FIG. 13 to which the subarray 1201A isconnected, the pads 1310B and 1310C of FIG. 13 to which the subarray1201B is connected, etc.). The fourth conductive layer 1120 may includepad 1030 of FIG. 13. The first conductive layer 1101 and the thirdconductive layer 1105 may be formed of Cu or other materials known toone of ordinary skill in the art. The second conductive layer 1103 maybe formed of tantalum nitride (TaN) or other materials known to one ofordinary skill in the art. The fourth conductive layer 1120 may beformed of aluminum (Al) or other materials known to one of ordinaryskill in the art. The fourth conductive layer is optional, as in certainapplications (such as for integrated sensors) the magnetic field sensingmodules 200 of FIG. 13 may be directly connected to other circuitry on achip.

FIG. 15 illustrates a top view of the portion 601 of the magnetic fieldsensing device 600 of FIG. 6 including a top view of the pair ofmagnetic field sensing modules 200A and 200E included in the portion 601of the magnetic field sensing device 600, according to an embodiment ofthe invention. FIG. 16 illustrates an expanded top view of the pair ofmagnetic field sensing modules 200A and 200E of FIG. 15, according to anembodiment of the invention. Each of the magnetic field sensing modules200A-200H includes a corresponding magnetic field sensing array100A-100H (see FIG. 6) that includes G subarrays 1501A-1501N of magneticfield sensing elements 102. Each of the G subarrays 1501 includes Np_subrows 1502A-1502N of magnetic field sensing elements 102 in parallel, andNs_sub magnetic sensing elements 102 per row 1202 connected in series.

As previously described with reference to FIGS. 9 and 10, the field line612 may be a single field line. Alternatively, the field line 612 mayrepresent multiple field lines 1012 in parallel. Also as previouslydescribed with reference to FIGS. 9 and 10, the serpentinecharacteristic of the field line 612 and the field lines 1012facilitates differential detection. In one embodiment, referring to FIG.2B, the DC bias current 210 of the magnetic field sensing module 200Aflows through the magnetic field sensing module 200A from a pad 1612 toa ground pad 1503, and the DC bias current 210 of the magnetic fieldsensing module 200E flows through the magnetic field sensing module 200Efrom a pad 1620 to the ground pad 1503. The differential voltage outputacross the magnetic field sensing modules 200A and 200E can be measuredas the difference between the voltage at the pad 1612 and the voltage atthe pad 1620.

There are a number of advantages of the magnetic field sensing array 100(including subarrays 1501) as used in the embodiment of FIGS. 15 and 16for high voltage applications (in one example, a 50 Volts to 100 Voltsoutput voltage requirement, though the range of voltages for theseapplications is not restricted to this range). As output voltagerequirements increase, Ns_sub tends to increase and Np_sub tends todecrease in the embodiment of FIGS. 12 and 13. This leads to an increasein the Ns_sub field lines 1012 needed in the embodiment of FIGS. 12 and13, which leads to an increase in the DC bias current 210 (see FIG. 2)needed, as the DC bias current 210 is divided between the Ns_sub fieldlines 1012. One approach to reduce the number of field lines 1012 is toorient the subarrays 1501 such that the current flow through each of therows 1502 is in substantially parallel to the current flow through aportion of the field lines 1012, such as but not limited to the portionof the field lines 1012 nearest to each of the rows 1502. In this way,the number of field lines 1012 can therefore be reduced from Ns_sub (inthe embodiment of FIGS. 12 and 13) to Np_sub, resulting in significantlyreduced output current and power requirements. For example, forNs_sub=10, Np_sub=4, and G=20, the output voltage and current permagnetic field sensing module 200 are 50 V to 100 V (for Rmin of 1 KΩand Rmax of 2 KΩ, respectively) and 2 mA, respectively.

In addition, due to the partitioning of the magnetic field sensingmodules 200 into the subarrays 1501, the robustness of the magneticfield sensing arrays 100 against failures of one or more magnetic fieldsensing elements 102 included in the magnetic field sensing arrays 100is increased relative to the embodiment of FIGS. 9 and 10, in a similarmanner to that previously described for the embodiment of FIGS. 12 and13.

Also, as previously described, the output power of the magnetic fieldsensing array 100 increases with the total number of magnetic fieldsensing elements 102 included in the magnetic field sensing array 100.The product G*Ns_sub*Np_sub can thereby be configured so that themagnetic field sensing device 600 meets output power requirements.

FIG. 17 illustrates an example of a response curve relating an outputsignal of the magnetic field sensing modules 200 in the embodiment ofFIGS. 15 and 16 to an input signal to the magnetic field sensing modules200 in the embodiment of FIGS. 15 and 16, according to an embodiment ofthe invention. The description of FIG. 17 is in many respects similar toFIG. 4, so only portions that are different are stated here. FIG. 17 isfor the structure of the magnetic field sensing modules 200 in theembodiment of FIGS. 15 and 16, which has Ns_sub=10, Np_sub=4, and G=20.In this example, the input DC current 130 (see FIG. 2B) is 10 mA(divided among 4 field lines 1012, as shown in FIG. 16), and the outputDC current 132 is 2 mA, as previously described with reference to FIGS.15 and 16. In this example, the output voltage is in the range from 50 Vto 100 V, as previously described with reference to FIGS. 15 and 16.

FIG. 18 also illustrates a perspective view of a portion 1800 of one ofthe pair of magnetic field sensing modules 200A and 200E of FIG. 16,according to an embodiment of the invention. In one embodiment, theportion 1800 includes, for a single row 1502 included in one of themagnetic field sensing modules 200 of FIG. 16, the pads (sections) 1610Aand 1610B, the magnetic field sensing elements 102, and the associatedconductive layers electrically connected and magnetically connected tothe magnetic field sensing elements 102. The portion 1800 includesmagnetic field sensing elements 1810A-1810N (in one embodiment,corresponding to the magnetic field sensing elements 102 of FIG. 16,which can be MTJs), a first conductive layer 1801 including conductiveinterconnects 1802A-1802N that are each connected to a corresponding oneor a pair of the magnetic field sensing elements 1810, a secondconductive layer 1803 including straps 1804A-1804N that are eachconnected to a corresponding pair of the magnetic field sensing elements1810, and a third conductive layer 1805 including field line 1806 (inone embodiment, corresponding to one of the field lines 1012 of FIG.16). The field line 1806 is magnetically coupled to each of the magneticfield sensing elements 1810 included in the portion 1800. In oneembodiment, the portion 1800 includes a fourth conductive layer 1820that may include sections 1610A-1610N (in one embodiment, including thepads 1610A and 1610B of FIG. 16 to which the subarray 1501A isconnected, the pads 1610B and 1610C of FIG. 16 to which the subarray1501B is connected, etc.). The fourth conductive layer 1820 may includepad 1030 of FIG. 16. The first conductive layer 1801 and the thirdconductive layer 1805 may be formed of Cu or other materials known toone of ordinary skill in the art. The second conductive layer 1803 maybe formed of tantalum nitride (TaN) or other materials known to one ofordinary skill in the art. The fourth conductive layer 1820 may beformed of aluminum (Al) or other materials known to one of ordinaryskill in the art. The fourth conductive layer is optional, as in certainapplications (such as for integrated sensors) the magnetic field sensingmodules 200 of FIG. 16 may be directly connected to other circuitry on achip.

Referring to FIGS. 1-18 and 20-21, in one embodiment, an apparatuscomprises a plurality of circuits, each of the plurality of circuitsincluding an array of magnetic tunnel junctions (such as the magneticfield sensing array 100 including the magnetic field sensing elements102) partitioned into a plurality of subarrays (such as the subarrays1201 of FIGS. 12 and 13 or the subarrays 1501 of FIGS. 15 and 16),wherein: the magnetic tunnel junctions in each of the plurality ofsubarrays are arranged in a plurality of rows (such as the rows 1202 ofFIGS. 12 and 13 or the rows 1502 of FIGS. 15 and 16), the magnetictunnel junctions in each of the plurality of rows are connected inseries, and the plurality of rows are connected in parallel; theplurality of subarrays are connected in series; and each magnetic tunneljunction includes a storage layer having a storage magnetization and asense layer having a sense magnetization, each magnetic tunnel junctionbeing configured such that the sense magnetization and impedance of eachmagnetic tunnel junction vary in response to an external magnetic field(such as the external magnetic field 140). The apparatus furthercomprises a module (such as the magnetic field determination module 502of FIG. 5) configured to determine the external magnetic field based ona parameter of each of the plurality of circuits, wherein the parameterof each of the plurality of circuits varies based on a combinedimpedance of the multiple magnetic tunnel junctions, the module beingimplemented in at least one of a memory or a processing device.

In one embodiment of the apparatus, the magnetic tunnel junctions in oneor more of the plurality of rows are disposed between a first conductivelayer (such as the first conductive layer 1101 of FIG. 11 or the firstconductive layer 1801 of FIG. 18) and a second conductive layer (such asthe second conductive layer 1103 of FIG. 11 or the second conductivelayer 1803 of FIG. 18) including a strap; a first magnetic tunneljunction, a second magnetic tunnel junction, and a third magnetic tunneljunction disposed between the first magnetic tunnel junction and thesecond magnetic tunnel junction are included in the magnetic tunneljunctions (such as the MTJs 1110 of FIG. 11 or the MTJs 1810 of FIG. 18)in the one or more of the plurality of rows; the first magnetic tunneljunction and the third magnetic tunnel junction are connected to aportion of the first conductive layer; and the second magnetic tunneljunction and the third magnetic tunnel junction are connected to thestrap. The strap may be formed of a different material than the firstconductive layer, and the strap may be thinner than the first conductivelayer.

In one embodiment of the apparatus, the apparatus further comprises afirst conductive layer including a first section (such as the section1310A of FIG. 13 or the section 1610A of FIG. 16), a second sectionphysically separated from the first section, and a third sectionphysically separated from the first section and the second section,wherein: the plurality of subarrays include a first subarray and asecond subarray adjacent to the first subarray; the first subarray isdisposed between the first section and the third section; and the secondsubarray is disposed between the second section and the third section.The third section may be disposed between the first subarray and thesecond subarray. The third section may be displaced from each of thefirst section and the second section in a first direction, and the thirdsection may be substantially parallel to the first section and thesecond section. The first section may be displaced from the secondsection in a second direction substantially perpendicular to the firstdirection.

In one embodiment, the apparatus further comprises a field line (such asthe field line 612 or the field lines 1012 of FIGS. 12, 13, 15, and 16)configured for a first current flow to traverse the field line andhaving a plurality of portions including a first portion (such asportion 622A of the field line 612 of FIG. 6) and a second portion (suchas portion 622B of the field line 612 of FIG. 6), wherein: the pluralityof circuits include a first circuit and a second circuit; the field lineis configured to generate a first magnetic field for configuring anoperating point of the first circuit based on the first current flowthrough the first portion of the field line; and a direction of thefirst current flow through the first portion of the field line issubstantially perpendicular to the first direction (such as in theembodiment of FIGS. 12 and 13). The direction of the first current flowthrough the first portion of the field line may be substantiallyperpendicular to a direction of a second current flow through one ormore of the plurality of rows of the first subarray (such as row 1202Aof subarray 1201A of FIG. 13), and to a direction of a third currentflow through one or more of the plurality of rows of the second subarray(such as subarray 1201B of FIG. 13). The direction of the second currentflow through the one or more of the plurality of rows of the firstsubarray may be substantially opposite to the direction of the thirdcurrent flow through the one or more of the plurality of rows of thesecond subarray.

In one embodiment of the apparatus, the field line is configured togenerate a second magnetic field for configuring an operating point ofthe second circuit based on the first current flow through the secondportion of the field line; and a direction of the first current flowthrough the second portion of the field line is substantially oppositeto the direction of the first current flow through the first portion ofthe field line. The apparatus may be configured to generate adifferential signal, the differential signal being a difference betweena first output signal of the first circuit (such as the magnetic fieldsensing module 200A of FIGS. 12 and 13) and a second output signal ofthe second circuit (such as the magnetic field sensing module 200E ofFIGS. 12 and 13), wherein a magnitude of the differential signal isincreased relative to the first output signal and the second outputsignal. The apparatus may be configured to generate the differentialsignal for suppression of common mode noise.

In one embodiment, the apparatus further comprises a second conductivelayer and a third conductive layer, wherein: the magnetic tunneljunctions in one or more of the plurality of rows included in the firstsubarray are disposed between the second conductive layer (such as theconductive layer 1101 of FIG. 11) and the third conductive layer (suchas the conductive layer 1103 of FIG. 11); a current flow through themagnetic tunnel junctions in the one or more of the plurality of rowsincluded in the first subarray traverses the second conductive layer andthe third conductive layer; and the second conductive layer and thethird conductive layer are oriented in a second direction substantiallythe same as the first direction.

In one embodiment of the apparatus, the third section is displaced fromthe first section in a first direction; the third section is displacedfrom the second section in a second direction substantially opposite tothe first direction; and the third section is substantially parallel tothe first section and the second section. The second section may bedisplaced from the first section in a third direction substantially thesame as the first direction.

In one embodiment, the apparatus further comprises a field line (such asthe field line 612 or the field lines 1012 of FIGS. 12, 13, 15, and 16)configured for a first current flow to traverse the field line andhaving a plurality of portions including a first portion (such asportion 622A of the field line 612 of FIG. 6) and a second portion (suchas portion 622B of the field line 612 of FIG. 6), wherein: the pluralityof circuits include a first circuit and a second circuit; the field lineis configured to generate a first magnetic field for configuring anoperating point of the first circuit based on the first current flowthrough the first portion of the field line; and a direction of thefirst current flow through the first portion of the field line issubstantially parallel to the first direction (such as in the embodimentof FIGS. 15 and 16). The direction of the first current flow through thefirst portion of the field line may be substantially parallel to adirection of a second current flow through one or more of the pluralityof rows of the first subarray (such as row 1502A of subarray 1501A ofFIG. 16), and to a direction of a third current flow through one or moreof the plurality of rows of the second subarray (such as subarray 1501Bof FIG. 16). The direction of the second current flow through the one ormore of the plurality of rows of the first subarray (such as subarray1501A of FIG. 16) may be substantially the same as the direction of thethird current flow through the one or more of the plurality of rows ofthe second subarray (such as subarray 1501B of FIG. 16).

In one embodiment of the apparatus, the field line is configured togenerate a second magnetic field for configuring an operating point ofthe second circuit based on the first current flow through the secondportion of the field line; and a direction of the first current flowthrough the second portion of the field line is substantially oppositeto the direction of the first current flow through the first portion ofthe field line. The apparatus may be configured to generate adifferential signal, the differential signal being a difference betweena first output signal of the first circuit (such as the magnetic fieldsensing module 200A of FIGS. 15 and 16) and a second output signal ofthe second circuit (such as the magnetic field sensing module 200E ofFIGS. 15 and 16), wherein a magnitude of the differential signal isincreased relative to the first output signal and the second outputsignal. The apparatus may be configured to generate the differentialsignal for suppression of common mode noise.

In one embodiment, the apparatus further comprises a second conductivelayer and a third conductive layer, wherein: the magnetic tunneljunctions in one or more of the plurality of rows included in the firstsubarray are disposed between the second conductive layer (such as theconductive layer 1801 of FIG. 18) and the third conductive layer (suchas the conductive layer 1803 of FIG. 18); a current flow through themagnetic tunnel junctions in the one or more of the plurality of rowsincluded in the first subarray traverses the second conductive layer andthe third conductive layer; and the second conductive layer and thethird conductive layer are oriented in a second direction substantiallythe same as the first direction.

In one embodiment, an apparatus comprises a plurality of circuitsincluding a first circuit and a second circuit, each of the plurality ofcircuits including a plurality of subarrays (such as the subarrays 1201of FIGS. 12 and 13) of magnetic tunnel junctions, wherein: the magnetictunnel junctions in each of the plurality of subarrays are arranged in aplurality of rows (such as the rows 1202 of FIGS. 12 and 13), themagnetic tunnel junctions in each of the plurality of rows are connectedin series, and the plurality of rows are connected in parallel; and theplurality of subarrays are connected in series. The apparatus furthercomprises a field line (such as the field line 612 or the field lines1012 of FIGS. 12 and 13) configured to generate a first magnetic fieldfor configuring an operating point of the first circuit based on acurrent flow through the field line, wherein impedance of one or more ofthe magnetic tunnel junctions in each of the plurality of rows of eachsubarray of magnetic tunnel junctions included in the first circuit isconfigured based on the first magnetic field.

In one embodiment of the apparatus, one or more of the magnetic tunneljunctions in each of the plurality of rows of each subarray of magnetictunnel junctions included in the first circuit is a first subset of themagnetic tunnel junctions in each of the plurality of rows of eachsubarray of magnetic tunnel junctions included in the first circuit. Thefield line may be a first field line (such as field line 1012A of FIG.13) and the current flow may be a first current flow. In one embodiment,the apparatus further comprises a second field line (such as field line1012B of FIG. 13) configured to generate a second magnetic field forconfiguring the operating point of the first circuit based on a secondcurrent flow through the second field line. Impedance of a second subsetof the magnetic tunnel junctions in each of the plurality of rows ofeach subarray of magnetic tunnel junctions included in the first circuitmay be configured based on the second magnetic field, and the secondsubset may be distinct from the first subset. The first field line andthe second field line may be serpentine.

In one embodiment of the apparatus, the apparatus further comprises afirst conductive layer including a first section (such as the section1310A of FIG. 13), a second section physically separated from the firstsection, and a third section physically separated from the first sectionand the second section, wherein: the plurality of subarrays include afirst subarray and a second subarray adjacent to the first subarray; thefirst subarray is disposed between the first section and the thirdsection; and the second subarray is disposed between the second sectionand the third section. The third section may be disposed between thefirst subarray and the second subarray. The third section may bedisplaced from each of the first section and the second section in afirst direction, and the third section may be substantially parallel tothe first section and the second section. The first section may bedisplaced from the second section in a second direction substantiallyperpendicular to the first direction.

In one embodiment of the apparatus, the field line (such as the fieldline 612 or the field lines 1012 of FIGS. 12 and 13) may have aplurality of portions including a first portion (such as portion 622A ofthe field line 612 of FIG. 6) and a second portion (such as portion 622Bof the field line 612 of FIG. 6); the current flow is a first currentflow through the first portion of the field line; and a direction of thefirst current flow through the first portion of the field line issubstantially perpendicular to the first direction (such as in theembodiment of FIGS. 12 and 13). The direction of the first current flowthrough the first portion of the field line may be substantiallyperpendicular to a direction of a second current flow through one ormore of the plurality of rows of the first subarray (such as row 1202Aof subarray 1201A of FIG. 13), and to a direction of a third currentflow through one or more of the plurality of rows of the second subarray(such as subarray 1201B of FIG. 13). The direction of the second currentflow through the one or more of the plurality of rows of the firstsubarray may be substantially opposite to the direction of the thirdcurrent flow through the one or more of the plurality of rows of thesecond subarray (such as subarray 1311 of FIG. 13).

In one embodiment of the apparatus, the field line is configured togenerate a second magnetic field for configuring an operating point ofthe second circuit based on the first current flow through the secondportion of the field line; and a direction of the first current flowthrough the second portion of the field line is substantially oppositeto the direction of the first current flow through the first portion ofthe field line. The apparatus may be configured to generate adifferential signal, the differential signal being a difference betweena first output signal of the first circuit (such as the magnetic fieldsensing module 200A of FIGS. 12 and 13) and a second output signal ofthe second circuit (such as the magnetic field sensing module 200E ofFIGS. 12 and 13), wherein a magnitude of the differential signal isincreased relative to the first output signal and the second outputsignal. The apparatus may be configured to generate the differentialsignal for suppression of common mode noise.

In one embodiment, the apparatus further comprises a second conductivelayer and a third conductive layer, wherein: the magnetic tunneljunctions in one or more of the plurality of rows included in the firstsubarray are disposed between the second conductive layer (such as theconductive layer 1101 of FIG. 11) and the third conductive layer (suchas the conductive layer 1103 of FIG. 11); a current flow through themagnetic tunnel junctions in the one or more of the plurality of rowsincluded in the first subarray traverses the second conductive layer andthe third conductive layer; and the second conductive layer and thethird conductive layer are oriented in a second direction substantiallythe same as the first direction.

In one embodiment of the apparatus, a first number of the magnetictunnel junctions in each of the plurality of rows are connected inseries; a second number of the plurality of subarrays are connected inseries; and a product of the first number and the second number (such asNs_sub*G of FIG. 13) is configured such that a voltage across eachmagnetic tunnel junction included in the array of magnetic tunneljunctions is in the range from about 0.25 volts to about 0.5 volts.Impedance of the array of magnetic tunnel junctions may be in the rangefrom about 2 kiloohms to about 8 kiloohms, and a voltage across thearray of magnetic tunnel junctions may be in the range from about 20volts to about 40 volts. A first number of the magnetic tunnel junctionsin each of the plurality of rows (such as Ns_sub of FIG. 13) may be inthe range from about 2 to about 8. A second number of the plurality ofsubarrays connected in series (such as G of FIG. 13) may be in the rangefrom about 10 to about 40. A product of the first number and the secondnumber (such as Ns_sub*G of FIG. 13) may be in the range from about 80to about 160. A third number of the plurality of rows connected inparallel (such as Np_sub of FIG. 13) in each of the plurality ofsubarrays may be in the range from about 20 to about 40.

In one embodiment of the apparatus, a first number of the magnetictunnel junctions in each of the plurality of rows are connected inseries; a second number of the plurality of subarrays are connected inseries; a third number of the plurality of rows are connected inparallel in the corresponding one of the plurality of subarrays; and aratio of a product of the first number and the second number to thethird number (Ns_sub*G/Np_sub of FIG. 13) is in the range from about 2to about 4.

In one embodiment, an apparatus comprises a plurality of circuitsincluding a first circuit and a second circuit, each of the plurality ofcircuits including a plurality of subarrays (such as the subarrays 1501of FIGS. 15 and 16) of magnetic tunnel junctions, wherein: the magnetictunnel junctions in each of the plurality of subarrays are arranged in aplurality of rows (such as the rows 1502 of FIGS. 15 and 16), themagnetic tunnel junctions in each of the plurality of rows are connectedin series, and the plurality of rows are connected in parallel; and theplurality of subarrays are connected in series. The apparatus furthercomprises a field line (such as the field line 612 or the field lines1012 of FIGS. 15 and 16) configured to generate a first magnetic fieldfor configuring an operating point of the first circuit based on acurrent flow through the field line, wherein impedance of a subset ofthe plurality of rows in each subarray of magnetic tunnel junctionsincluded in the first circuit is configured based on the first magneticfield.

In one embodiment of the apparatus, the field line may be a first fieldline (such as field line 1012A of FIG. 16) and the current flow may be afirst current flow. In one embodiment, the apparatus further comprises asecond field line (such as field line 1012B of FIG. 16) configured togenerate a second magnetic field for configuring the operating point ofthe first circuit based on a second current flow through the secondfield line. The subset may be a first subset. Impedance of a secondsubset of the magnetic tunnel junctions in each of the plurality of rowsof each subarray of magnetic tunnel junctions included in the firstcircuit may be configured based on the second magnetic field, and thesecond subset may be distinct from the first subset. The first fieldline and the second field line may be serpentine.

In one embodiment of the apparatus, the apparatus further comprises afirst conductive layer including a first section (such as the section1610A of FIG. 16), a second section physically separated from the firstsection, and a third section physically separated from the first sectionand the second section, wherein: the plurality of subarrays include afirst subarray and a second subarray adjacent to the first subarray; thefirst subarray is disposed between the first section and the thirdsection; and the second subarray is disposed between the second sectionand the third section. The third section may be disposed between thefirst subarray and the second subarray. The third section may bedisplaced from each of the first section and the second section in afirst direction, and the third section may be substantially parallel tothe first section and the second section.

In one embodiment of the apparatus, the third section (such as thesection 1610B of FIG. 16) may be displaced from the first section in afirst direction; the third section may be displaced from the secondsection (such as the section 1610C of FIG. 16) in a second directionsubstantially opposite to the first direction; and the third section maybe substantially parallel to the first section and the second section.The second section may be displaced from the first section in a thirddirection substantially the same as the first direction.

In one embodiment of the apparatus, the field line (such as the fieldline 612 or the field lines 1012 of FIGS. 15 and 16) may have aplurality of portions including a first portion (such as portion 622A ofthe field line 612 of FIG. 6) and a second portion (such as portion 622Bof the field line 612 of FIG. 6); the current flow is a first currentflow through the first portion of the field line; and a direction of thefirst current flow through the first portion of the field line issubstantially parallel to the first direction (such as in the embodimentof FIGS. 15 and 16). The direction of the first current flow through thefirst portion of the field line may be substantially parallel to adirection of a second current flow through one or more of the pluralityof rows of the first subarray (such as row 1502A of subarray 1501A ofFIG. 16), and to a direction of a third current flow through one or moreof the plurality of rows of the second subarray (such as subarray 1501Bof FIG. 16). The direction of the second current flow through the one ormore of the plurality of rows of the first subarray may be substantiallyparallel to the direction of the third current flow through the one ormore of the plurality of rows of the second subarray.

In one embodiment of the apparatus, the field line is configured togenerate a second magnetic field for configuring an operating point ofthe second circuit based on the first current flow through the secondportion of the field line; and a direction of the first current flowthrough the second portion of the field line is substantially oppositeto the direction of the first current flow through the first portion ofthe field line. The apparatus may be configured to generate adifferential signal, the differential signal being a difference betweena first output signal of the first circuit (such as the magnetic fieldsensing module 200A of FIGS. 15 and 16) and a second output signal ofthe second circuit (such as the magnetic field sensing module 200E ofFIGS. 15 and 16), wherein a magnitude of the differential signal isincreased relative to the first output signal and the second outputsignal. The apparatus may be configured to generate the differentialsignal for suppression of common mode noise.

In one embodiment, the apparatus further comprises a second conductivelayer and a third conductive layer, wherein: the magnetic tunneljunctions in one or more of the plurality of rows included in the firstsubarray are disposed between the second conductive layer (such as theconductive layer 1801 of FIG. 18) and the third conductive layer (suchas the conductive layer 1803 of FIG. 18); a current flow through themagnetic tunnel junctions in the one or more of the plurality of rowsincluded in the first subarray traverses the second conductive layer andthe third conductive layer; and the second conductive layer and thethird conductive layer are oriented in a second direction substantiallythe same as the first direction.

In one embodiment of the apparatus, a first number of the magnetictunnel junctions in each of the plurality of rows are connected inseries; a second number of the plurality of subarrays are connected inseries; and a product of the first number and the second number (such asNs_sub*G of FIG. 16) is configured such that a voltage across eachmagnetic tunnel junction included in the array of magnetic tunneljunctions is in the range from about 0.25 volts to about 0.5 volts.Impedance of the array of magnetic tunnel junctions may be in the rangefrom about 50 kiloohms to about 100 kiloohms, and a voltage across thearray of magnetic tunnel junctions may be in the range from about 50volts to about 100 volts. A first number of the magnetic tunneljunctions in each of the plurality of rows (such as Ns_sub of FIG. 16)may be in the range from about 5 to about 40. A second number of theplurality of subarrays connected in series (such as G of FIG. 13) may bein the range from about 5 to about 40. A product of the first number andthe second number (such as Ns_sub*G of FIG. 16) may be in the range fromabout 200 to about 400. A third number of the plurality of rowsconnected in parallel (such as Np_sub of FIG. 13) in each of theplurality of subarrays may be in the range from about 4 to about 8.

In one embodiment of the apparatus, a first number of the magnetictunnel junctions in each of the plurality of rows are connected inseries; a second number of the plurality of subarrays are connected inseries; a third number of the plurality of rows are connected inparallel in the corresponding one of the plurality of subarrays; and aratio of a product of the first number and the second number to thethird number (Ns_sub*G/Np_sub of FIG. 16) is in the range from about 45to about 55.

In one embodiment, an apparatus comprises a plurality of groups ofmagnetic tunnel junctions (examples of the magnetic field sensingelements 102), wherein the magnetic tunnel junctions in each group arearranged in a plurality of rows, the magnetic tunnel junctions in eachof the plurality of rows are connected in series, and the plurality ofrows are connected in parallel. The apparatus further comprises a firstconductive layer (such as the first conductive layer 1101 of FIG. 11 orthe first conductive layer 1801 of FIG. 18) including a plurality ofconductive interconnects; a second conductive layer (such as the secondconductive layer 1103 of FIG. 11 or the second conductive layer 1803 ofFIG. 18) including a plurality of straps; and a third conductive layer(such as the third conductive layer 1105 of FIG. 11 or the thirdconductive layer 1805 of FIG. 18) including a plurality of field lines(such as the field line 612 or the field lines 1012 of FIGS. 9, 10, 12,13, 15, and 16), each of the plurality of field lines configured togenerate a magnetic field for configuring an operating point of acorresponding subset of the magnetic tunnel junctions in each groupbased on a current flow through each of the plurality of field lines.The magnetic tunnel junctions in each group is disposed between andconnected to a corresponding one of the plurality of conductiveinterconnects and a corresponding one of the plurality of straps. Thesecond conductive layer is disposed between the first conductive layerand the third conductive layer. Each of the plurality of field lines maybe serpentine. Each of the plurality of groups of magnetic tunneljunctions may be a subarray of magnetic tunnel junctions (such as thesubarrays 1201 of FIGS. 12 and 13 or the subarrays 1501 of FIGS. 15 and16). The plurality of groups of magnetic tunnel junctions may beconnected in series.

In one embodiment, the apparatus further comprises a fourth conductivelayer (such as the fourth conductive layer 1120 of FIG. 11 or the fourthconductive layer 1820 of FIG. 18) including a plurality of sections,wherein the plurality of rows in each group are disposed between andconnected to a corresponding pair of sections included in the pluralityof sections. The plurality of groups may include a first group and asecond group. The plurality of sections may include a first section, asecond section, and a third section. For the first group, thecorresponding pair of sections may include the first section and thethird section. For the second group, the corresponding pair of sectionsmay include the second section and the third section. The third sectionmay be connected to the plurality of rows in the first group and theplurality of rows in the second group. The third section may be disposedbetween the first section and the second section. The third section maybe displaced from each of the first section and the second section in afirst direction. The third section may be substantially parallel to thefirst section and the second section. The first section may be displacedfrom the second section in a second direction substantiallyperpendicular to the first direction.

In one embodiment of the apparatus, impedance of the plurality of groupsof magnetic tunnel junctions connected in series is in the range fromabout 2 kiloohms to about 8 kiloohms; and a voltage across the pluralityof groups of magnetic tunnel junctions connected in series is in therange from about 20 volts to about 40 volts.

In one embodiment of the apparatus, impedance of the plurality of groupsof magnetic tunnel junctions connected in series is in the range fromabout 50 kiloohms to about 100 kiloohms; and a voltage across theplurality of groups of magnetic tunnel junctions connected in series isin the range from about 50 volts to about 100 volts.

In one embodiment of the apparatus, the third section may be a groundpad (such as the ground pad 903 of FIG. 10 or the ground pad 1203 ofFIG. 12) disposed between the first section and the second section.

In one embodiment of the apparatus, each of the plurality of straps maybe formed of a different material than each of the plurality ofconductive interconnects. Each of the plurality of straps may be thinnerthan each of the plurality of conductive interconnects.

In one embodiment of the apparatus, the plurality of groups may includea first group and a second group. Each of the plurality of field linesmay include a first portion (such as portion 622A of the field line 612of FIG. 6) configured to generate the magnetic field for configuring theoperating point of the corresponding subset of the magnetic tunneljunctions in the first group based on the current flow through the firstportion of each of the plurality of field lines. The first portions ofthe plurality of field lines may be substantially parallel (such as thefield lines 1012 of FIGS. 9, 10, 12, 13, 15, and 16). Each of theplurality of field lines may include a second portion (such as portion622B of the field line 612 of FIG. 6) configured to generate themagnetic field for configuring the operating point of the correspondingsubset of the magnetic tunnel junctions in the second group based on thecurrent flow through the second portion of each of the plurality offield lines. The second portions of the plurality of field lines may besubstantially parallel to the first portions of the plurality of fieldlines. A direction of the current flow through the first portion of eachof the plurality of field lines may be substantially opposite to adirection of the current flow through the second portion of each of theplurality of field lines.

In one embodiment, the apparatus further comprises a fourth conductivelayer (such as the fourth conductive layer 1120 of FIG. 11 or the fourthconductive layer 1820 of FIG. 18) including a conductive pad, wherein:the first portions of the plurality of field lines (such as portion1022A of field line 1012A and portion 1023A of field line 1012B in FIGS.10, 13, and 16) are connected in parallel; the second portions of theplurality of field lines (such as portion 1022B of field line 1012A andportion 1023B of field line 1012B in FIGS. 10, 13, and 16) are connectedin parallel; and the first portions of the plurality of field lines areconnected to the second portions of the plurality of field lines by theconductive pad (such as conductive pad 1030 in FIGS. 10, 13, and 16).

In one embodiment, each of the plurality of field lines may include asecond portion configured to generate the magnetic field for configuringthe operating point of the corresponding subset of the magnetic tunneljunctions in the second group based on the current flow through thesecond portion of each of the plurality of field lines. The secondportions of the plurality of field lines may be substantially parallel.The second portions of the plurality of field lines (such as portion622C of the field line 612 of FIG. 6) may not be substantially parallelto the first portions of the plurality of field lines.

In one embodiment, a direction of the current flow through the firstportion of each of the plurality of field lines may be substantiallyperpendicular to a direction of a current flow through each of theplurality of rows in the first group.

In one embodiment, a direction of the current flow through the firstportion of each of the plurality of field lines may be substantiallyperpendicular to a direction of a current flow through each of theplurality of rows in the first group.

In one embodiment, a direction of the current flow through the firstportion of each of the plurality of field lines may be substantiallyparallel to a direction of a current flow through each of the pluralityof rows in the first group.

In one embodiment, a direction of the current flow through the firstportion of each of the plurality of field lines may be substantiallyopposite to a direction of a current flow through each of the pluralityof rows in the first group.

FIG. 19 illustrates a logical block diagram of a system 1900 fortransmission and reception of a signal encoded in a quadrature modulatedmagnetic field, according to an embodiment of the invention. An inputsignal 1902 is amplified by amplifier 1904, then is applied to modulator1906. The modulated output of the modulator 1906 is applied to magneticfield generator 1908 to generate a modulated magnetic field thatpropagates over transmission medium 1910. The magnetic field is receivedand sensed by the magnetic field sensing module 200 (previouslydescribed with reference to FIGS. 1-18). The output of the magneticfield sensing module 200 is then demodulated by demodulator 1912 toobtain output signal 1914.

There are various potential applications for the system 1900, such asunderwater communication, near-field communication, communication overlocal area networks (LANs), direct broadcast, and flashing (such as forsecure wireless firmware updates). As the communication is over amagnetic field rather than an electrical field, there can be advantagessuch as enhanced security and immunity to RF interference. The bandwidthof the input signal 1902 and the output signal 1914 can be in the tensof MHz or higher, such as in the GHz range, as the frequency response ofthe magnetic field sensing elements 102 (see FIG. 1) included in themagnetic field sensing module 200 can be in those ranges. The system1900 can therefore be used, for example, for transmitting audio, video,and data. The magnetic field sensing module 200 also detects themagnetic field, including amplitude, phase, and directional information.This enables use of modulation approaches that encode the input signal1902 in either or both the amplitude and phase of the modulated signal,such as but not limited to quadrature amplitude modulation. This is anadvantage of the magnetic field sensing module 200 over a solenoid,which detects magnetic flux and can lose phase information in thereceived magnetic field. Also, the magnetic field sensing module 200 canact as a magnetic antenna, so a separate coil is not needed. Theseparate coil can be costly, bulky, and senses in only one direction,while the magnetic field sensing module 200 can sense in multipledirections.

In one embodiment, the magnetic field sensing module 200 may be aportion of the magnetic field sensing device 600 of FIG. 6, such as themagnetic field sensing module 200A. Alternatively, the system 1900 mayinclude the magnetic field sensing device 600 of FIG. 6 (which includesmultiple magnetic field sensing modules 200 at different angularorientations) for sensing the transmitted magnetic field. The system1900 may include additional modules, such as those described in thecontext of FIG. 5. Any of the various structures described in FIGS. 1-18for magnetic field sensing can be used as the magnetic field sensingmodule for the system 1900.

In one embodiment, an apparatus comprises a circuit (such as themagnetic field sensing module 200 of FIG. 19) including multiplemagnetic tunnel junctions (examples of magnetic field sensing elements102 of FIG. 1), the circuit configured to convert a quadrature modulatedmagnetic field to a quadrature modulated electrical signal, eachmagnetic tunnel junction including a storage layer having a storagemagnetization and a sense layer having a sense magnetization, eachmagnetic tunnel junction being configured such that the sensemagnetization and impedance of each magnetic tunnel junction vary inresponse to the quadrature modulated magnetic field. The apparatusfurther comprises a module configured to demodulate the quadraturemodulated electrical signal to recover a signal encoded in thequadrature modulated magnetic field. The circuit may be a first circuitand the quadrature modulated electrical signal may be a first quadraturemodulated electrical signal. The apparatus may further comprise a secondcircuit (such as the magnetic field sensing module 200E of FIG. 6)including multiple magnetic tunnel junctions, the circuit configured toconvert the quadrature modulated magnetic field to a second quadraturemodulated electrical signal. The module (such as the demodulator 1912 ofFIG. 19) may be configured to perform combining based on the firstquadrature modulated electrical signal and the second quadraturemodulated electrical signal to recover the signal. The combining may beone of equal-gain combining, maximal-ratio combining, switchedcombining, and selection combining, or any other form of diversitycombining known to one of ordinary skill in the art. The advantages arerealized with immunity to eavesdropping and rate of decay of a magneticsignal over distance.

In one embodiment of the apparatus, an operating point of the circuit isconfigured such that for a first subset of the multiple magnetic tunneljunctions, the sense magnetization is substantially aligned with thestorage magnetization at the operating point, and for a second subset ofthe multiple magnetic tunnel junctions, the sense magnetization issubstantially anti-aligned with the storage magnetization at theoperating point.

In one embodiment of the apparatus, each magnetic tunnel junction isconfigured such that impedance of each magnetic tunnel junction variesin response to an amplitude and a phase and frequency of the quadraturemodulated magnetic field. The signal may be an audio signal. The signalmay be a media signal including one or more of a video signal and anaudio signal.

In one embodiment of the apparatus, the quadrature modulated electricalsignal may be quadrature amplitude modulated. The quadrature modulatedelectrical signal may be quadrature amplitude modulated based on one ofa 16-QAM constellation, a 64-QAM constellation, and a 256-QAMconstellation, or on any other QAM constellation known to one ofordinary skill in the art.

In one embodiment, the apparatus further comprises a first plurality ofcircuits, wherein: the circuit is a first circuit; a second plurality ofcircuits includes the first circuit and the first plurality of circuits;each of the second plurality of circuits (such as the magnetic fieldsensing modules 200A-200H of FIG. 6) has a distinct angular orientation;and each of the first plurality of circuits includes multiple magnetictunnel junctions, each magnetic tunnel junction being configured suchthat impedance of each magnetic tunnel junction varies in response tothe quadrature modulated magnetic field. The apparatus may furthercomprise a field line (such as the field line 612 of FIG. 6 or the fieldlines 1012 of FIGS. 9, 10, 12, 13, 15, and 16) configured to generate amagnetic field for configuring an operating point of each of the secondplurality of circuits based on a current flow through the field line,wherein the field line includes a plurality of portions, each of theplurality of portions disposed adjacent to a corresponding one of thesecond plurality of circuits, and each of the plurality of portionsbeing configured such that the current flow through each of theplurality of portions has an angular orientation corresponding to thedistinct angular orientation of the corresponding one of the secondplurality of circuits. The angular orientations of the plurality ofportions of the field line may be substantially equally spaced. Theplurality of portions of the field line may include N portions (such asportions 622A, 622B, and 622C of the field line 612 of FIG. 6), whereinN is at least three. The angular orientations of the plurality ofportions of the field line may be substantially equally spaced by anangle of 360 degrees divided by N.

In one embodiment, the plurality of portions of the field line mayinclude a first portion and a second portion. The current flow throughthe first portion may be in a substantially opposite direction to thecurrent flow through the second portion. The first plurality of circuitsmay include a second circuit. The field line may be configured togenerate the magnetic field for configuring an operating point of thefirst circuit based on the current flow through the first portion of thefield line. The field line may be configured to generate the magneticfield for configuring an operating point of the second circuit based onthe current flow through the second portion of the field line.

In one embodiment, the apparatus may be configured to generate adifferential signal, the differential signal being a difference betweena first output signal of the first circuit (such as the magnetic fieldsensing module 200A of FIGS. 6, 9, 10, 12, 13, 15, and 16) and a secondoutput signal of the second circuit (such as the magnetic field sensingmodule 200E of FIGS. 6, 9, 10, 12, 13, 15, and 16), wherein a magnitudeof the differential signal is increased relative to the first outputsignal and the second output signal. The apparatus may be configured togenerate the differential signal for suppression of common mode noise.

In one embodiment, the operating point of each of the second pluralityof circuits is configured to substantially maximize gain of thecorresponding one of the second plurality of circuits.

In one embodiment, the operating point of each of the second pluralityof circuits is configured to maintain substantially linear operation ofthe corresponding one of the second plurality of circuits.

FIG. 20 illustrates an apparatus 2000 configured in accordance with oneembodiment of the present invention. The apparatus includes a centralprocessing unit (CPU) 2002 connected to a bus 2006. Input/output devices2004 may also be connected to the bus 2006, and may include a keyboard,mouse, display, and the like. An executable program representing amagnetic field determination module 502 (see FIG. 5) as described abovecan be stored in memory 2008. Executable programs representing othermodules included in the magnetic field sensing devices 500 and 600 (seeFIGS. 5 and 6) can also be stored in the memory 2008.

FIG. 21 illustrates an apparatus 2100 configured in accordance withanother embodiment of the present invention. The apparatus 2100 includesa field programmable gate array (FPGA) and/or an application specificintegrated circuit (ASIC) 2102 that implements the operations of themagnetic field determination module 502 and/or other modules included inthe magnetic field sensing devices 500 and 600 (see FIGS. 5 and 6). TheFPGA/ASIC 2102 may be configured by and may provide output toinput/output devices 2104.

An embodiment of the invention relates to a computer-readable storagemedium having computer code thereon for performing variouscomputer-implemented operations. The term “computer-readable storagemedium” is used herein to include any medium that is capable of storingor encoding a sequence of instructions or computer codes for performingthe operations described herein. The media and computer code may bethose specially designed and constructed for the purposes of theinvention, or they may be of the kind well known and available to thosehaving skill in the computer software arts. Examples ofcomputer-readable storage media include, but are not limited to:magnetic media such as hard disks, floppy disks, and magnetic tape;optical media such as CD-ROMs and holographic devices; magneto-opticalmedia such as floptical disks; and hardware devices that are speciallyconfigured to store and execute program code, such asapplication-specific integrated circuits (“ASICs”), programmable logicdevices (“PLDs”), and ROM and RAM devices. Examples of computer codeinclude machine code, such as produced by a compiler, and filescontaining higher-level code that are executed by a computer using aninterpreter or a compiler. For example, an embodiment of the inventionmay be implemented using Java, C++, or other object-oriented programminglanguage and development tools. Additional examples of computer codeinclude encrypted code and compressed code. Moreover, an embodiment ofthe invention may be downloaded as a computer program product, which maybe transferred from a remote computer (e.g., a server computer) to arequesting computer (e.g., a client computer or a different servercomputer) via a transmission channel. Another embodiment of theinvention may be implemented in hardwired circuitry in place of, or incombination with, machine-executable software instructions.

While the invention has been described with reference to the specificembodiments thereof, it should be understood by those skilled in the artthat various changes may be made and equivalents may be substitutedwithout departing from the true spirit and scope of the invention asdefined by the appended claims. In addition, many modifications may bemade to adapt a particular situation, material, composition of matter,method, or process to the objective, spirit and scope of the invention.All such modifications are intended to be within the scope of the claimsappended hereto. In particular, while the methods disclosed herein havebeen described with reference to particular operations performed in aparticular order, it will be understood that these operations may becombined, sub-divided, or re-ordered to form an equivalent methodwithout departing from the teachings of the invention. Accordingly,unless specifically indicated herein, the order and grouping of theoperations are not limitations of the invention.

What is claimed is:
 1. An apparatus, comprising: a plurality of groupsof magnetic tunnel junctions, wherein the magnetic tunnel junctions ineach group are arranged in a plurality of rows, the magnetic tunneljunctions in each of the plurality of rows are connected in series, andthe plurality of rows are connected in parallel; a first conductivelayer including a plurality of conductive interconnects; a secondconductive layer including a plurality of straps; a third conductivelayer including a plurality of field lines, each of the plurality offield lines configured to generate a magnetic field for configuring anoperating point of a corresponding subset of the magnetic tunneljunctions in each group based on a current flow through each of theplurality of field lines; wherein: the magnetic tunnel junctions in eachgroup are disposed between and connected to a corresponding one of theplurality of conductive interconnects and a corresponding one of theplurality of straps; and the second conductive layer is disposed betweenthe first conductive layer and the third conductive layer; wherein: eachof the plurality of groups of magnetic tunnel junctions is a subarray ofmagnetic tunnel junctions; and the plurality of groups of magnetictunnel junctions are connected in series; and a fourth conductive layerincluding a plurality of sections, wherein the plurality of rows in eachgroup are disposed between and connected to a corresponding pair ofsections included in the plurality of sections.
 2. The apparatus ofclaim 1, wherein each of the plurality of field lines is serpentine. 3.The apparatus of claim 1, wherein: the plurality of groups includes afirst group and a second group; the plurality of sections include afirst section, a second section, and a third section; for the firstgroup, the corresponding pair of sections includes the first section andthe third section; for the second group, the corresponding pair ofsections includes the second section and the third section; and thethird section is connected to the plurality of rows in the first groupand the plurality of rows in the second group.
 4. The apparatus of claim3, wherein the third section is disposed between the first section andthe second section.
 5. The apparatus of claim 3, wherein: the thirdsection is displaced from each of the first section and the secondsection in a first direction; the third section is substantiallyparallel to the first section and the second section; and the firstsection is displaced from the second section in a second directionsubstantially perpendicular to the first direction.
 6. The apparatus ofclaim 1, wherein: impedance of the plurality of groups of magnetictunnel junctions connected in series is in the range from about 2kiloohms to about 8 kiloohms; and a voltage across the plurality ofgroups of magnetic tunnel junctions connected in series is in the rangefrom about 20 volts to about 40 volts.
 7. The apparatus of claim 1,wherein; impedance of the plurality of groups of magnetic tunneljunctions connected in series is in the range from about 50 kiloohms toabout 100 kiloohms; and a voltage across the plurality of groups ofmagnetic tunnel junctions connected in series is in the range from about50 volts to about 100 volts.
 8. An apparatus, comprising: a plurality ofgroups of magnetic tunnel junctions, wherein the magnetic tunneljunctions in each group are arranged in a plurality of rows, themagnetic tunnel junctions in each of the plurality of rows are connectedin series, and the plurality of rows are connected in parallel; a firstconductive layer including a plurality of conductive interconnects; asecond conductive layer including a plurality of straps; a thirdconductive layer including a plurality of field lines, each of theplurality of field lines configured to generate a magnetic field forconfiguring an operating point of a corresponding subset of the magnetictunnel junctions in each group based on a current flow through each ofthe plurality of field lines; wherein: the magnetic tunnel junctions ineach group are disposed between and connected to a corresponding one ofthe plurality of conductive interconnects and a corresponding one of theplurality of straps; and the second conductive layer is disposed betweenthe first conductive layer and the third conductive layer; and a fourthconductive layer including a plurality of sections, wherein theplurality of rows in each group are disposed between and connected to acorresponding pair of sections included in the plurality of sections. 9.The apparatus of claim 8, wherein: the plurality of groups includes afirst group and a second group; the plurality of sections include afirst section, a second section, and a third section; for the firstgroup, the corresponding pair of sections includes the first section andthe third section; for the second group, the corresponding pair ofsections includes the second section and the third section; and thethird section is connected to the plurality of rows in the first groupand the plurality of rows in the second group.
 10. The apparatus ofclaim 9, wherein the third section is a ground pad disposed between thefirst section and the second section.
 11. The apparatus of claim 8,wherein: each of the plurality of straps is formed of a differentmaterial than each of the plurality of conductive interconnects; andeach of the plurality of straps is thinner than each of the plurality ofconductive interconnects.
 12. An apparatus, comprising: a plurality ofgroups of magnetic tunnel junctions, wherein the magnetic tunneljunctions in each group are arranged in a plurality of rows, themagnetic tunnel junctions in each of the plurality of rows are connectedin series, and the plurality of rows are connected in parallel; a firstconductive layer including a plurality of conductive interconnects; asecond conductive layer including a plurality of straps; a thirdconductive layer including a plurality of field lines, each of theplurality of field lines configured to generate a magnetic field forconfiguring an operating point of a corresponding subset of the magnetictunnel junctions in each group based on a current flow through each ofthe plurality of field lines; wherein: the magnetic tunnel junctions ineach group are disposed between and connected to a corresponding one ofthe plurality of conductive interconnects and a corresponding one of theplurality of straps; and the second conductive layer is disposed betweenthe first conductive layer and the third conductive layer; and wherein:the plurality of groups includes a first group and a second group; eachof the plurality of field lines includes a first portion configured togenerate the magnetic field for configuring the operating point of thecorresponding subset of the magnetic tunnel junctions in the first groupbased on the current flow through the first portion of each of theplurality of field lines; and the first portions of the plurality offield lines are substantially parallel.
 13. The apparatus of claim 12,wherein: each of the plurality of field lines includes a second portionconfigured to generate the magnetic field for configuring the operatingpoint of the corresponding subset of the magnetic tunnel junctions inthe second group based on the current flow through the second portion ofeach of the plurality of field lines; the second portions of theplurality of field lines are substantially parallel to the firstportions of the plurality of field lines; and a direction of the currentflow through the first portion of each of the plurality of field linesis substantially opposite to a direction of the current flow through thesecond portion of each of the plurality of field lines.
 14. Theapparatus of claim 13, further comprising a fourth conductive layerincluding a conductive pad, wherein: the first portions of the pluralityof field lines are connected in parallel; the second portions of theplurality of field lines are connected in parallel; and the firstportions of the plurality of field lines are connected to the secondportions of the plurality of field lines by the conductive pad.
 15. Theapparatus of claim 12, wherein: each of the plurality of field linesincludes a second portion configured to generate the magnetic field forconfiguring the operating point of the corresponding subset of themagnetic tunnel junctions in the second group based on the current flowthrough the second portion of each of the plurality of field lines; thesecond portions of the plurality of field lines are substantiallyparallel; and the second portions of the plurality of field lines arenot substantially parallel to the first portions of the plurality offield lines.
 16. The apparatus of claim 12, wherein a direction of thecurrent flow through the first portion of each of the plurality of fieldlines is substantially perpendicular to a direction of a current flowthrough each of the plurality of rows in the first group.
 17. Theapparatus of claim 12, wherein a direction of the current flow throughthe first portion of each of the plurality of field lines issubstantially parallel to a direction of a current flow through each ofthe plurality of rows in the first group.
 18. The apparatus of claim 12,wherein a direction of the current flow through the first portion ofeach of the plurality of field lines is substantially opposite to adirection of a current flow through each of the plurality of rows in thefirst group.